To toss in my two pennies, I fall somewhere between Boxer and Fixer here (and, like everyone else, feel that the RAW back up my position).
On p. 128 of the core book, there is a level 45 spell, Fog of Confusion, that is MuAu with a ReIm requisite. I think it's pretty fair to characterize this as a spell which does two pretty distinct things to its target (the fog) (note: I do think the raw is clear that all effects of a spell must share Range, Target, and Duration): changes the makeup of the fog, and makes it start giving off strange noises. To me, that seems pretty comparable to the notion of, say "makes this person over here both invisible and able to fly".
However, if you look at the makeup for said spell, in includes: "+1 Imaginem requisite, +1 Rego Requisite". To me, this, combined with the Spell chapter section on Requisites, give the impression that requisites are thought of in terms of art, not in terms of Technique/Form combination.
In the case of the triple pilum of flame, the way I tend to think of it is, basically, as a requisite: it's a CrIg spell with two additional Ig effects; since they add an effect, and aren't simply cosmetic, each incurs the +1 magnitude for an additional effect. Thus, it works out to being functionally equivalent to a complexity bump. Three different damage rolls would be made, and soak would apply to each separately. Sometimes, this will be better than simply casting the larger more damaging effect; sometimes, it won't.
I would say that assuming that any requisite addition for additional effect also automatically adds a complexity bump as well is over-the-top, and not supported by the RAW.
So, I'd say, yes, you can combine distinct effects into a single spell, as long as requisites are taken into account separately. (And, that, additional effects in addition to the ones you took the requisite for in the first place add +1 magnitude, keeping in mind that on p.114, it does specifically note that the largest-magnitude effect is the one that the spell is based on... you can't cheat and add-on a big requisite effect on a little basic spell.)
So, the hypothetical invisible flying magi spell:
PeIm R:Per, D:Con, T:Ind: Base 4, +1 changing Image
ReCo: R:Per, D:Con, T:Ind: Base 15 (I'm assuming the speedy flight)
So, the ReCo effect is bigger, so that's our base.
Re(Pe)Co(Im) 30: R:Per, D:Con, T:Ind
Allows a magus to fly invisibly.
(Base 15, +1 Con, +1 Pe Req, +1 Im Req)
To the naysayers, I would note that such a spell is vastly harder than its parts. A magus willing to learn two spells would need to be able to handle ReCo 20 and PeIm 10; the magus trying to learn this spell needs to be able to handle both ReCo 30 and PeIm 30.