@Z: I'm not really making myself clear... what I mean is, I don't really know in advance what familiar I want for a given quest step. Do you? It depends on if I need mana, HP, stats (the usual), blocking, or...? Arguably it's most useful to change familiars within a quest, like grabbing a potato for a boss, but that's a whole 'nother level of complexity. So there may be a common set of optimizations that applies all the time, but if there is, I don't know about it.
So I'd have to ship a data file with it, which I generally hate doing because they inevitably have compatibility issues when you make changes in the code to add or remove a field, and I don't see how it helps much.
Now all that said, if someone wants to put up a list of what familiar is best for each questlevel, I'll happily reconsider (and probably learn a thing or two in the process). But it adds complexity, so I probably won't get to it unless I can see how it's a real help.