Actually, MuCo Base 2 give the target a minor ability. Not a minor magical ability.
It's an ability granted by magic, and isn't naturally possessed by humans. Sounds magical to me. Same goes for having a +6 to Str. It's still an extrapolation, which is probably why that person went with the Base 25 instead of Base 2 for Hercules' Gift; as it's obviously more than just "can see well in poor lighting", but it's more 'natural' than breathing fire which you can grant horses.
There's a difference between a mundane ability, but which is unnatural for the target to have, and a magical ability. Don't confuse the source of the ability with the nature of the ability.
Thus, giving a horse the ability to breathe is not done through MuAn alone; it requires a requisite for the ability. Neither is it a minor change -- it requires a much higher base than simply changing the horse in an unnatural (but still strictly physical) way.
"Being better" is usually an expression of what is possible for the target's natural form. You can enhance that with Creo magic, permanently if it is a ritual. When you try to exceed what is natural for the target, then you have to move to Muto -- and the more unnatural the change, the higher the base.
Regrowing limbs is natural for lizards, as is blood hot enough to melt diamonds for a he-goat. Mythic Europe explicitly blurs the lines between mundane and magical, making an attempt to differentiate difficult. However, this doesn't seem like a very relevant point, because nobody is advocating for super strength to be Base Level 2.
And? I'm not sure what your point is here, because you are giving the tone of explaining something that we're misunderstanding...by repeating our conclusions to use Muto and to have a higher Base Level than 2.
Well, I was initially answering only to this comment from you:
It seemed to me that you were suggesting that Base 2 could be used as a basis to grant someone the equivalent of a minor virtue (such as Great Characteristics).
This seems like it was not what you were suggesting. My apologies for adding noise to the discussion!
All that being said, using MuCo (dare I extend this to MuMe?) to grant a boot to a characteristic to make it 6+ will likely cause a lot of warping. Sure, the magus can always cast it on himself, and avoid the warping from the high level effect, but he will still have to deal with a nearly constant effect. Certainly use of a spell in a season of lab activity would be employing the warping rules from Covenants (which I generally prefer)...
I wouldn't think that's so certain. That sounds like double-counting. The magus is getting warped, not the lab. Do you do the same for any magus with a longevity ritual, warping the lab as well? Do you additionally penalize a magus with an active healing spell for recovery? Plus there is no suggestion in Covenants that using spells to keep the magus alert and awake for the season (which explicitly warps the magus) warps the lab, which seems to be a similar type thing.
The magus presumably doesn't receive warping on himself for spells he casts, they were invented. Warping for other recipients is what I was talking about in reference to the warping problemsAnd as far as spells and warping, serf's Parma, doesn't addled take this into account?
Could one avoid the warping issue by incorporating it into the familiar bond?
I believe it would remove the personal warping, sure.
I'm less sure on the lab warping rules, in this instance because the familiar bond mimics the invested device, which wouldn't raise the lab's warping score, however, I'm generally opposed to the idea of boosting human characteristics beyond 5, anyway, so I'd tend to rule that it would raise the warping score, despite what the rules suggest.
There are much better ways to add a +1 (or more) bonus to the lab total (which is when this would come into effect for the lab). Those bonuses would also be permanent and, IMO, better aligned to the magus.