Yea, I just thought of the trouble with cross-mod compatibility as well. If it could inherit villager/village classes, that would help avoid that, but if it can't, the only way I can think of, other than making villager hooks and requesting other mod authors edit THEIR code to be compatible (always a BAD idea, IMO) would be to have some way of detecting other mods looking up the relevant classes and redirect them.
It *might* be possible for the village/villager classes to simply be a re-direct to your own, but I don't know how viable that would be in Java. That would be incredibly kludgy, though... it would feel like using GOTO...