As much as I can see the reason behind this request (I’ve written networked movement comps’ for two games now, which includes simple sphere collision to complex vehicle collision) - a lot of CMC’s functionality is based on the fact that a character can be represented by a Capsule.
If you think about it though, you’d still need to write your own movement component for quadruped movement. Quad’s can do a lot of things that bipeds can’t, so even if CMC supported multiple collision primitives - the movement would still feel like a biped.
A preferable option, would be to split CMC’s code off into segments so that it can be reused for other movement components. This is pretty hard to do though, and will most likely break backward compatibility. I’ve had a bit of luck with it.