Hmm, now you have me thinking. A hermetic alchemist making a magical familiar (like a homonculus). That sounds kind of cool. And my best Arts are already Creo and Vim. Hmm. There's potential here.
Where are the rules on animating things to create things like a revenant or a magical creature/item?
We're officially a "High" Power saga, so the base Magic Might should be ≈15 or ≈5. The other is just spitballing what is possible under the rules with his abilities.
Wouldn't it be hard to get a Bonding Total of 67 out of gauntlet with all those prerequisites?
Still, I'm really liking the idea of a homonculus familiar ...
Huh? You are confusing the Bonding Total to make the thing a familiar with the Lab Total to invent the ritual. In the latter case, she's well below 67, though the Vim requisite really isn't an issue.
Quite possibly.
Now where is the general ritual described? I can't figure out which book to look in.
I think it's one he's inventing.
So, I am entirely in the realm of conjecture here, based largely on the few posts made about this. But would the following ritual be at all valid?
Create Homonculus
CrHe(Me,Vi) 20r
Animates a man-shaped bundle of wood into a homonculus of Might up to 20. The Vim requisite makes the homonculus magical, while the Mentem requisite makes it intelligent. A Corpus requisite could be added to make the resulting homonculus look like a person and not a bundle of sticks.
(Base 20)
Presumably Te could replace He for a homonculus made of clay.
I realize we're limited to Might 15 for familiars. But a ritual must be at minimum level 20, so it has to be designed for up to a 20 Might. In practice, the created homonculus would actually have a Might of 15 if it were being used as a familiar.
The minimum base for creating beings with Might is usually much higher. Elementals are the sole exception of which I'm aware, and even those are higher.
Where are the rules for this located? It would be much easier for me to just read those rules than play blind man's bluff with proposals. 
I don't want to be a pain, but isn't creating a creature with true intellect very hard; as in bordering on the hermetic limits? I realise that you're probably creating a creature with cunning and not Int, then it gets Int from the bond. Still?
Really I'm doing this for the coolness factor of having a hermetic alchemist with a homonculus as a familiar. (I assume the same would be true for Beatrix with an animated familiar). From what I can see, numerically, a homonculus will be pretty darn close to a magical animal. A few qualities will be different. But largely they'd look similar. The only difference is that it will take more effort to get a homonculus familiar than a magical animal. (I'm willing to take some kind of a hit for the coolness factor.)
That having been said, if it's too much of a pain to get a homonculus familiar, or if it violates the rules, then I can always go back to having a magical animal familiar and have functionally the same result, but without the coolness factor. I was just trying to do something different than the same old, same old of getting a magical animal as a familiar.
I'm a fan of what you're both doing, great ideas and I asked in that very neutral manner because it would be cool and it would be a shame if you couldn't. I was just thinking about the similar effects and was pondering how I'd do it.
Interesting note: I was looking at the lesser device The Marvelous Hound in Covenants for Rise of Atlantis, and noted that it creates Intelligence from Cunning. So clearly creating intelligence is not outside the bounds of hermetic magic.
Look at the CrAn guidelines in ArM5. A later book references those same rules for CrCo (and some of the Corpus stuff in ArM5 specifically says to reference Animal stuff). Following that, I would expect CrHe to be similar.
Creating beings with Cunning is straight from the original book of the line, ArM5. There are examples of its application later. Turning Cunning into Intelligence -3 is straight from the original book as well.
This, and there was something in Broken Covenant of Calebais. The Calebais one required original research to have been done. I don't know about this collar.
Ah, there it is. But a CrHe(Me,Vi) 50r ritual to get a Might 15 familiar is a total non-starter. Sadly, it's far easier to take the traditional route and gain a magic animal as a familiar just like everyone else does. I'm afraid the rules stand in the way of creativity.
A CrHe(Me,Vi) 50r ritual to get a familiar with -3 Int. Even better.
Again, I don't mind taking a little bit of a hit for the coolness factor of a homonculus familiar rather than a magical animal familiar. (And it really is just coolness factor, since the functional difference between the two would be close to nil.) But if the rules will impose a great penalty on that concept, then I'll just take the common way out and go with a magical animal.
I understand. I've been debating if I should just start with the familiar bound already. Avoiding creating the familiar from scratch helps me a lot. With MM15 Beatrix could bind a Size +5 familiar straight out of gauntlet. There is no question she can pull off Size +6 before game start since she's so close already. But I also wanted to put seasons into working on her talisman, lots of seasons. I may well go the same route as you, though. I need to see...
Well, look at that... Magic Animal reduces Might by Size, so MM15 becomes MM8 with Size+7. 25+5x7+8=68. Beatrix was certainly headed past 70 by game start.
BTW, is there some limit to what we may choose as our familiars? I mean, could I just choose to have a dragon or a phoenix familiar or must I stick with relatively 'common' beasts like animals of virtue?
Spirits and elementals need a virtue. Not sure about mythical beasts might be the same.