A bit of creative scaling and tinting might turn an umberhulk into a mezzoloth.
You might turn a wraith (or a deathknight in one of the hooded robes) into Charon.
The boobed were-badger (ie. 'werewolf') might be scaled slightly and tinted red-orange to make a raavasta (albeit a naked female one). I've toyed with the idea of using it as a werefox (perhaps in a "What's killing the chickens?" quest). Or a gnome/halfling level 1 druid who got stuck halfway while trying to wildshape into a badger for the first time. I'd use it for ANYTHING other than an actual werewolf. 
Most of the other yugoloths look fairly unique, and would probably require new models.