I usually blame 'legacy spells' on experimentation side effects and modified effects, or on the weird Insight lab texts you get when integrating old traditions, such as the various traditions that were combined to form the basis of the Order.
But cloak of flame and blade of the virulent flame both rely on a guideline built specifically for that purpose right in the Creo Ignem guidelines list, which suggests that it was intentional that hermetic magic allow that, and it seems to unnecessarily cut off a large number of options to say that it can't. The +1 magnitude implicit in the Creo Ignem guidelines suggests similar should be required for 'unnatural effect' when using other guidelines, of course.
"+1 Complexity" is a standard hand-wave solution to a lot of problems like this, and more than one canon spell enjoys its generously undefined umbrella. I was just hoping to avoid that if it was possible.
I think I am accurate in my understanding of the rules. Target can refer to the either the material affected by the spell or the target of the spell. Rewrite your spell to affect target : room. Does it not become clear that the "target" is the room you cast the spell at, not the air affected by the spell? Page 133, "A spell with target Room is useless if there is no Room containing the targets; it cannot a "roughly room-sized volume" in open space.". Even your example is tricky as it is Target : individual, and speaks of the damage done to the individual it hits. I think it is clear that the amounts given for "individual" at the front of each form is there for a base-line amount created by Creo spells, not to imply that there are no other targets. Obviously you don't read it that way.
How does Circling Winds of Protection work? It seems with a Rego requisite you should be able to accomplish what you want. The target affects the form and Rego should tether it, so I think you're all good. Akin to the "root you in your saddle" spells I've been thinking over lately.
It the target was supposed to be the head, no dice. Then the form/target are off and we run into the reason most curses don't work for hermetics.
As is, I think you're mildly overthinking it, and there are some examples to back it up.
At some point, you're got to let the magic into the spell, the sense of power and wonder. I often get sucked into more rules debates than attempts to make magic come alive, so i'm trying to stop. I think the spell you describe is cool, is backed up be examples in the RAW, and should not be a confounding problem for hermetic magic in the same way a 'spell to make birds hate you wherever you go' is.
You're one of the foremost rules masters on the board, but I think in this case your desire for this spell is being second guessed by the rules-mind, possibly.
I suppose there needs to be a more defined set of strata for "allowed by hermetic magic RAW" vs. "judgement call/saga decision as to whether this is a violation of hermetic theory as constructed by the RAW" vs. "breaks hermetic magic's limits by the RAW".
My personal thought, given that spectrum has an element of judgement/opinion in it, is that the spell seems fine to me.
My two florins,
Vrylakos
Here we go again: a difference between Target and target. Been discussed at length here several times. @CH: weren't you one of the main actors in that debate? I thought so...
Anyway, I would interpret that the target is The air around the head (Target: part) and that it targets air (target: Auram). Pretty much like the Target individual for creo ignem spells that coat a dude in flames. Add a Rego requisite for the air to move with the Target and you should be fine here. In other spells it works like that to keep the spell affecting the original Target without spreading or doing what it wants intead of what you want (again, ignem is a good section to look here). Hope that helps.
Cheers,
Xavi
I see…
But if someone else makes the same suggestion…
I think you just have it in for me and automatically disregard anything I say.
And…
And again, when others make the same or similar suggestions (such as Xavi or Ejidoth), then suddenly it is transformed from “complete gibberish of (my) own manufacture” into an idea worthy of consideration.
Is it just when I say it then? What do you have against me?
Wait, never mind. I already know.
As long as you don’t write me any more long PM’s about how I am intentionally trying to destroy the game, I am cool. I have thick skin and I love to argue, so bring it on 
And yes, you can use Rego to make a rock stick to someone all day, even after leaving your sight. If that is what the spell is designed to do, it will stick for long as the Duration of the spell allows. A spell doesn’t expire just because you stopped looking at it. If I use MuCo to turn you into a crow and you fly away, you are still stuck as a crow until the spell expires. I don’t have to watch you. If I use ReTe to make a stone platform float for a Duration of Moon, I can go home, go to bed, come back next week, and the stone platform will still be floating there.
Just fine, thanks for asking! 
Certainly possible - I've done it before.
But I was as much interested to see if there was any rationale in canon, more than if there were legacy examples and handwaves to be made. There isn't, so I know I'm on my own.
Which means I want to think it out long and hard, so that other spells stay consistent without setting a fatal precedent. Which I've seen happen all too often.
I mean, if it works with that spell, then it should with other CrAu's too, right?
The Invisible Fewmet
CrAu 15
Creates a foul stench that follows a person around all day long.
(Base 3, +2 Voice, +2 Diameter)
Another cool spell... so if it works on Aurum, then it should work with Aquam in water, right? And if in water, then out. And we've seen it on Ignem, then the other element, Terram. And if Terram then Herbam. And the Forms too, right?... Right??...
So you can us CrIm to create an illusion that follows someone else around automatically. Not "on" them, but just near/around them, the same distance as a cloud. Like an illusory dog following them about. Or use Creo/Rego Animal to create actual birds fluttering about the person's head all day long - or all Moon! Because that's how this spell works, right? 
Hmmm... what about Terram... and if not, why not? (Besides "cuz I say so now shaddup!")
A slippery slope. 
All perfectly kosher spells under my reading of the RAW. Where is the problem with these? Add a rego requisite (+1 magnitude) and there you go. Your spell is +2 sun, not +2 diameter, BTW 
Xavi
I conccur. Perfectly legit and RAW.
I'd just chip in that unless you're creating something which by its nature cannot move relative to a victim (much easier than Target/target) such as a rock, I have to problem with position being defined relative to something else. Casting a spell "around a rock" means the spell stays around the rock. If you want something which might resist movement (a rock, for instance) to move then a Rego requisite is required. As far as the OP's spell goes, it's a Rego spell keeping air in place relative to the caster, so it doesn't need even that.
Frankly, to do otherwise requires an insane multiplication of spell parameters. You'd need Actor, Direct Target, Indirect Target, Nominative, Accusative, Ablative .... ::grins::
don't forget Genitive, the best, because these are Genies!
Damned Iberian Moorish Sympathisers! Where's a Flambeau when you need one?
Points at Marko
Cheers,
Xavi
No books with me, so I can't double check, but does the sword ignem spell have a Te requisite. It would seem to me that the target is fire, but by implication it is also the sword. Perhaps a house rule about 'target tethering' with requisites. Have to think about it.
Then there is the other problem of Parma. Put that air around a mage with parma (other than yourself) and then you're left with the unfortunate phenomenon that he can't breath it through parma. Could be used offensively - rego the are around his head (indirect) and suffocate him because air under an active magical effect can't bypass his parma. Great way to get him to drop it. Of course he could fast cast a 'competing' rego effect.
If you look at Lamp Without Flame, it creates light "centered on a point indicated by the caster. This point may be a mobile item". One more spell that follow a mobile target. Or look at all the Imaginem spells with a Tough range : the Target is Imaginem, but the target is the thing or person touched. Although in the case of Imaginem, it requires at least a +1 magnitude is the target can move without breaking the spell.
Personally, I think that allowing the bubble of air to be tethered to a person is not unreasonable. I would require a +1 Magnitude unless the spell was of Concentration duration, in which case I would rule that the caster's concentration is enough.
(Flaiming sword - no Te req)
Well, then I look forward to someone answering the question that I've posed several times already, but remains conveniently ignored each time:
What is the difference, Hermetically, between 1) a stinky CreoAurum effect (or fog cloud, or whatever) cast around a person, and 2) the identical stinky CreoAurum effect that follows a person around?
Without Rego, how does it (or any of these spells) follow anything, or move at all?
As for the other spells, canon or otherwise, the rules state that Rego can change the location of an object - but don't give any automatic connection to a moving reference point, like a person, sword or other object. "A spell that allows the caster to control the effect only permits that control as long as the caster is within range." Not "within range" of the person or object, but of the caster.
I'm not saying I don't like these spells, I'm not saying I don't allow them - I'm saying that we're all winking at the lack of a clear explanation in Hermetic terms.
Hey - you're right, I was! (Wow, a year later...) But it was not so much a "debate" as a common confusion. (see below)
And on that note, I was dismissive to Saxonous, and I formally apologize for that - sorry, Sax, my bad. 
But in order to claim to "understand" the rules, one has to understand (among other things) that a Target and a target are not the same thing*, nor intended to be by the editors, and that confusion is second only to the use of the word "Level" in another RPG that will not be named here. It's understandable and common, but I was talking about only one, and Saxonous was confusing both indiscriminately.
With Respect to Xavi's superior long-term memory that jogged my own, here is a thread that might prove useful in this matter:
(* There are actually, at least, 4 distinct and separate uses of the term "target/Target", but atm I am only referring to "the T/target of a spell".)
"What is the difference, Hermetically, between 1) a stinky CreoAurum effect (or fog cloud, or whatever) cast around a person, and 2) the identical stinky CreoAurum effect that follows a person around?"
I would say there is no difference Hermetically, save the first one targets (small t) an area, and the second one targets (small t) a thing. In canon, Hermetic magic "understands" the difference between locations and things, as shown by our categories of Targets; part, individual vs. Room, Structure, Boundary. Perhaps an early Breakthrough allowed Spells to "follow" their targets (small t).
No difference. One is cast on a location, around a guy. The other is cast on a location that has a guy at its centre and follows the guy around. Hence the need froer a rego requisite. othewise the guy moves, and the stinky cloud remains in the same place.
Xavi
I wouldn't require the Rego requisite myself. I'd require Rego for forced movement (ie. A circling rock), but centreing the effect on a mobile objest doesn't seem unreasonable to me. To answer the question then, the difference is that one is cast on a place (probably the patch of earth) and one on a person, no more and no less. The Hermetic Parameters of spells are of necessity simplified. Doubtless a magus, on the fly, takes into account many things when specifying target, range and what have you, but if you really want to calculate based on that many variables, your game will slow to a crawl.
Cloak of Fire isn't in either of 4th or 3rd ed. basic rules. As far as I know, it's new for 5th. So that argument might not fly. 