So thinking about anima magic, I've seen plenty of discussion re the mechanics but not a lot re the code. The magus has no control over the faeries he creates, whether they are transformed, summoned, or created from nothing, though he may be able to have a friendly relationship depending on the magus and the type of faerie. In response to that, it's a relatively simple matter to invent a ReVi spell to control them; but isn't that a blatant code violation? Especially if the faerie is summoned, rather than created, so goes back to the Faerie Realm when the duration is over, angry that you controlled it?
I see this as quite limiting to the utility of Anima magic, if you don't control it, you're left with social skills to charm and persuade or bargain with it; or the other good use I see is as a way to defend against hostile spells by transforming the spells into Vim faeries that wander off, or that you can be warded against.
The other thing I wonder about is the specificity of spell design - I get that you can't design the precise faerie you want, but are you limited to the broad definition in the guideline, or can you define a more specific role or type?
It's arguable as to whether it's a blatant code violation, but you would be pushing your luck. Does their vengeance catch your sodales?
Bargaining with faeries is covered by Faerie Lore (RoP:F pg 14), which Merinita will usually have good scores in.
The books are inconsistent on how specific you can be with your anima. Despite the HoH:MC rules being pretty restrictive, there are NPCs which have spells that summon faeries with clearly defined characteristics; see Patronus on pg 121 of Tales of Power, for example.
I'd probably rule that you can call forth a particular type of "existing" faerie, but the character can't just design a faerie that exactly meets their needs. So find an existing bit of folklore and say you want to summon a brownie, rather than saying you want to create a faerie with Power X and Virtue Y.
I have to wonder if one could use craft ability to design a faerie glamour before causing it to manifest with anima magic... hard to argue that it is closed to the artist before it exists...