Hmmm. Applause for the effort, but based not only on IRL biomechanics but how others have tried to replicated ungulates to plantigrades, your best bet does seem to be 1:1 translation to joints for movement. That is, from what you've got: move the ankle up onto a platform/high-heel. Just based on this pic: you've got the knee in the right place for MLP-latest but the thing is that their calves are almost nonexistantly short. Definitely nails the outline but in movement it won't look right.

Consider: Where the knee is on the human-in-the-exo: the human knee bends backwards and the calf is quite long and then the ankle; the upright-pony would have the knee there, but calf is almost comically short and then into the very long foor and toe (hoof) giving it the concept of bending the other way at the knee.

This is actually one of those things I've been contemplating for years so please do feel free to PM/Note me I'd be happy to help attempt to engineer something.

Hey, I appreciate the offer to help. I agree the biomechanics don't exactly sync up perfectly, and the ankles are always the hardest part to line up when building a creature suit. Of course, this isn't a perfect 1:1 look at what I'm working on, these will be tailored specifically to the wearer so they match up the locomotion better. This is more a general look on a generic model. There's also a few trade secrets involved not shown in this render, heh.

I get what you mean though, I've had to make monster and even dinosaur suits for films and productions before, and getting an inner framework to bend correctly around a suit actor's movements is a nightmare.

Yeah, the real proper horror is getting the fact that human calves are freakishly long and human feet are absurdly short compared to damn near every other animal ever.

You did for sure nail the still stance looking correct, which is nearly (in my personal opinion) as important as the in-motion look correct.