Sorry in advance for bothering you.
As the title says, currently the sheepmen are just wandering in Nether like those pigmen and skeletons. And thorn(1 kind of plant spawned by BOP) on the floor can kill them easily even if they are already immune to magma block, fire and lava.
Maybe make them only spawn in nether fortress may be a good idea? Since this mod is mob-oriented so adding structure might not be a god idea...anyway, that's all I think.
Also, add a way to breed them might me nice(like the villagers or?), and since they do have wool, add 1 point of armor to it might be good but too trivial.