For example: "Character Creation for Plot_Device (OOC)"
Yes. Though grogs are more held in common, so just because I create a specific grog doesn't mean you cannot play him for a specific story.
There should be troupe discussions about companions at some point also, since we will want to create companions that won't, as far as possible, interact with our magus. So we may look at companion concepts that are good fit with the magi of other players, and a bad fit with our own.
I was actually thinking of a version of teleportation that I want to hear the groups' thoughts on.
Teleportation through water. Ie linking two lakes or waterways, walking into one, then appearing out of the other. An arcane connection would be needed of course, and I reckon it would be ReCo(Aq), but probably thematically more akin to the focus of Aquam.
My initial thought is that this sounds more like Hermes Portal (ReTe 75), rather than the regular ReCo teleportation spells. Unfortunately, that also sounds like something that would require Original Research (or at least a very favourable result from Experimentation).
A thematical ReCo(Aq) spell sounds nice too (for flavour and aesthetics), but the Focus wouldn't provide any benefits.
I know this is a question of some controversy... what do we think about MuCo giving abilities like Immunities? Do other transformations (like changing the body to living wood or stone or metal) achieve whatever would be the inherent Immunities of such materials?
They should achieve some, yes. For example, if you are made of mist, weapons will pass right through you. But you shouldn't just be able to MuCo yourself to be able to replace CrIg, for example. This would be along the lines of the earlier debate about MuAu to make mist.
From my experience, a good rule of thumb is: if you have to explain the rationale for the improvement, it probably isn't appropriate. Of course being coated in duck's feathers would make you resitant to rain, but would they keep you warm?
For effects of a more powerful nature, I have no problem with another art taking a back seat if the transforming magic is of a higher magnitude. The benefit invariably comes with RP complications so if a +1 Strength is worth walking around with bear arms (terrible example), and the magnitude is at least what you would need with a CrCo equivalent, I don't have a problem.
I would say that having a duck's feathers would keep you warm because duck feathers keep you warm even when they are wet. They wouldn't create or radiate heat like fire does though.
I would think that transforming your body into mist or stone would do exactly those things. Mist might make you immune to being cut by a sword, but I would think it would make you very vulnerable to a strong wind. I don't think we need to represent that with a change in virtues or flaws, I think we can use qualitative descriptions that achieve such effects for the most part.
What kinds of immunities are we talking about getting here?