could one teach by a process of craft magic- substituting finesse+int for teaching+com? What level of ReMe would that require? It would have to be a season of work at minimum which means +6 to target...
Not by default, no. Teaching is specifically showing someone want to do, and supervising their practice. It's about communicating what you know effectively. Changing it from Com + Teaching would be a house rule. Though not necessarily an unworkable one.
Saying that, this sounds a lot more like Training (which does use the ability you're teaching), and would certainly work for improving someone's Finesse while you used your craft magic to build whatever.
If you're looking to improve someone's Arts, though, we're back to house rules (Training specifically forbids Hermetic Arts), and I don't know how you'd go about translating a scale used for Abilities to Arts. Not impossible, but I couldn't offer a suggestion I'd be happy with without doing a lot of test math first.
Not by the rules in the books. That would be a campaign specific rule to agree upon with your troupe.
Before discussing with them, show them
Note, that Hermetic craft magic spells and effects, as described in Covenants p.49 box Rego Craft Magic and HoH:S p.60f, are conventional spellcraft in the sense of the above quote. Note also, that such craft magic can replicate
, but it is a mulligan to extend this to teaching or training.
So it would be a good Bonisagus project...
Not quite what you're looking for, but I would expect magi to be able to study the products of craft magic to learn Finesse in the same way an artist can study art using the rules from A&A.
This, along with the already mentioned training should be the limit.
No. Since it's tailored for the student, it costs no warping. Tailored effects only Warp if they're long-term.
If this is done for more than two seasons a year, one could argue that it's an ongoing effect, though.