I like the pink dot Idea. In fact two of my Characters have a similar spell. But I do not like the fact that a Bjornaer in Bear form is resisted. I think I have to find a good house rule to deal with it.
A bjornear in Heart Beast shape is not resisted - only the transformation is magical, not the shape, which is natural and innate to the bjornear.
This is not a pink-dot issue, it is a feature of the Bjornear mystery.
The Longevity Ritual, now that could be a resistable effect though.
The [strike]pint[/strike] point is that a magus is under an active magical effect, and people/things under active magical effects need to penetrate resistance. So a magi, who is under the effects of a LR, by a string reading of RAW should have to penetrate, if you're brawling.
Like I said, callen can probably thread the logic needle better than I, all I can think of are active and passive effects, but I can come up with dozens of coutnerexamples (to myself) of why that won't fly. There needs to be some adjudication here of what each troupe is willing to accept as far as how MR operates.
Does MR just negate magical effects, but the physical properties (such as a sword's base damage) come through? It's not RAW, but it's probably the best HR I've seen that addresses this particular issue related to magic resistance.
I guess that depends upon how you interpret the rules. The way I see it, the Longevity effects of other traditions do need to Penetrate, but Hermetic and Folk Witch Longevity Rituals do not. This is because I only assume something is a supernatural effect that needs to Penetrate if it is (or would be, for those things you add to the game yourself) represented by a spell guideline or supernatural skill. The reason I take this interpretation is that there are no rules to calculate the Penetration of the Longevity Ritual, implying that such a formula is unnecessary as the LR doesn't need to Penetrate. This is further supported by the fact that all of the (extremely few) non-guideline/ability-based supernatural processes that require Penetration have how to calculate it listed right next to them, where the LR does not.
But anyway, YSMV.
Well, maybe that could make you feel better, callen. If we go Pink Dot without my Virtue/Supernatural-only intepretation, then the 100-year-old with the bear isn't any weaker than the young one with the trout, because they're both walled by their own Parma. 
I like that!
A Bit Pragmatic…....but nice and playable 
All of which can be obviated by the fact that Hermetic magi can lower their magic resistance...
It's been a bit of discussion on the list with anyone with MR can lower their MR, or if it is another feature of Parma Magica (that enhances collaboration and cooperation that other traditions can't match).
How does their ability to lower their MR obviate any part of what I said? The crux of my argument is that the LR doesn't comply with any existing Penetration formula, implying that Penetration isn't part of what happens.
I'm just saying that because the formula doesn't include anything about needing to penetrate doesn't mean that the effect doesn't need to penetrate. The alternative position is that the magus consuming the LR simply lowers his resistance so that the LR takes effect. Once under the effect of the LR, he can raise his Parma and be fully protected AND be under the effects of the LR.
You are jumping to a conclusion that has an alternative that is equally possible under the RAW.
I still have a small problem with my invisible giant.
Let´s take an unconscious Magus lying somewhere around. Now the friendly invisible giant comes around and wants to help. He tries to lift up the Magus carefully. Is he able to do that? I would like to say yes.
But what is than happening if the unfriendly invisible giant comes and finds the Magus instead of the friendly one. He also should be able to lift the Magus. If he can lift him he will also be able to throw him down the nearby cliff.
Friendly invisible giant can not lift the magus, by my reading. Sucks to be that magus.
@Jonathan.Link: I did say it depends on how you've interpreted it. I was never trying to call my way the only right way, and I think considering the LR to be a constantly active effect that needs to Penetrate is valid; I'm just pointing out that there are equally valid alternate readings that don't make a "by the book" magus weaker just for having a Longevity Ritual.
And I'm pointing out that 2 different elements are being conflated.
As for the Heartbeast, (and other shapeshifters, please see the box, p. 22 of HoH: MC.
I also openly concede that Longevity Rituals might be relevantly different.
callen is indeed a very gifted person.
I disagree. I like the pink dot, or perhaps rather the version of the pink dot where the magic has to be meaningfully relevant to the "weapon" being stopped, ie. Blunting the Iron's Bite from MoH.
Even though that leaves other problems.
Except that by your rule any magus with a familiar would need to penetrate to punch someone since there is a Hermetic guideline for that, even if isn't vanilla Hermetic magic.
I was thinking about starting a new thread just to collect magic resistance interpretations, which would give different effective answers to the OP and similar. For this thread, at least the OP has been answered including ramifications of some of the answers.
Then you would probably prefer an interpretation where the pink dot defense fails, and there are several of those.
Not... Exactly? If I'm understanding what you're saying, there is a guideline for a spell or somesuch in non-vanilla Hermeticism that emulates the Familiar binding process. So using that alternate method would require Penetration (I would guess...? I haven't seen what you're talking about before) but Familiars bound using the core rules would not bestow such a flaw upon their magus.
Though hilariously, this would still leave the initial complaint solved, since Bjornaer can't bind Familiars... 
Seems to me that the invisible giant-blooded grog (either one) would be able to pick the magus up with no problems.
The invisible giant-blooded grog is neither "created" nor "sustained" by magic, thus he is not a "magical thing" and can affect the magus without penetrating resistance. Similarly, his movements are entirely mundane, thus the motion need not penetrate.
If, however, the grog were normal-sized and magically transformed (MuCo) into a giant-sized grog, then I would agree that he's unable to move the magus, as his increased size would be "sustained" by magic, making him a "magical thing".
Where is the difference in being invisible PeIm and being increased size MuCo? Both are assumed to be hermetical effects. A normal grog with a pink dot would be a possible substitute to the invisible giant grog
In the MuCo case the grog's body is not his own. It is a body "created and sustained by magic." In the PeIm case the grog's body is his own and is not sustained by magic, magic has just caused its image to disappear. This is part of where the room for interpretation arises. There is no single correct answer. Rather, one should know the ramifications of one's choices and know that a choice must be made. This is how I do it and may well work as desired here:
I rule the same way callen does, though after reading about it I think going pink dot with Lucky's LR interpretation is also valid.
So in the case of the invisible grog, the parts of them within the Parma's bounds would become visible, but otherwise they could physically interact with the magus normally.
Invisibility is, as you said, PeIm. Its form is Imaginem. The grog is not Imaginem, thus a PeIm effect cannot change the grog himself. The grog's form is Corpus, thus he can be changed by MuCo.
If you really wanted to, I suppose you could create a PeIm(Co) version of invisibility which prevents its target from throwing off species in the first place[1] and such an effect would require the recipient to penetrate magic resistance, as the Corpus requisite would allow you to alter the Target himself. But I don't see any real reason or benefit in doing so. Adding the requisite limits the targets you could potentially affect and it has no obvious benefits other than making the Target subject to magic resistance, which could be done more easily with PeCo than PeIm(Co). Not to mention the drawback of "if I want my parma to prevent this guy from hitting me, why am I making him invisible?".
In practical terms, this seems to work out the same as callen's interpretation[2], even though we arrived there by different means.
[1] A later entry in the list of magic resistance examples on ArM5 p.86 says that resistance doesn't let you see invisible people because the species are destroyed before reaching a viewer, implying that they are still thrown, even if they can never be perceived.
[2] A MuTe boulder, Edge of the Razor, and MuAq poison would all be stopped because the form matches the boulder/sword/poison, but a flaming sword is a CrIg effect on a Te object and a mind-reading talisman is a Mentem effect on a non-Mentem object, so the base objects would be unaffected by resistance.
That's exactly what I meant.