60 is a TON, but I imagine they all use the same skeleton, or series of sized skeletons, so the models of them just need to be roughly the same in limb-size and thickness. I presume they will share all animations between em all other than a few "bosses", but you could add a little flair of individuality by doing stuff like different cum colors for exotic ones, different speeds for them (like a energetic monster may pound you super fast), different voice pitches or sounds, and facial expressions. May also be able to add some behavioral differences for mating, like a tough, very durable monster may breed you twice in a row before being satisfied, a large slow monster may cum for 2-3 times as long as normal ones, while maybe some small, feisty one could do something like rapid-fire climaxes with just a few thrusts between then ending, or a very "full" monster causing extra cum-filling/slow-down when finishing.
Just throwing ideas at the wall, see if any stick! Lots of ways to make characters feel unique without having to make new animations or skeletons, just tweak the animation cycles and results of.
...I admit some of these ideas are biased, as I'm a breeding and futa-centric sub, but many of these should work with people of other interests too.
