:(
so the only solution would be straightened legs? too bad.
Unfortunately for now, but even then the tail would be stiff unless using Liztail's Animation Kit. (Can you even use the upright beast option without the race being marked as beast in the first place? Last I knew, the animkit only took a beast race and made the feet mesh conform to the upright skeleton.)
It's totally doable though, it's no different from the normal BB skeleton aside from a few extra bones. (If using Liztail's better beasts.) Believe me, I know, I've been working a lot in Blender and I've actually been trying my hands at making a proper animation set for the Khajiit and Argonians. I'm not very fast at learning so I'm making little to zero progress. Rigging is about the only thing I know how to do in Blender and I know very little of it.
I too would love to see a talented modder make a nicer animation set for them, but I doubt it'll happen. Not many people seem willing to give it a try, like DarkDiva said. :/ It's a shame, it's one of the last few things that really need updating. That and Dagoth Ur, although I believe DU is being worked on.
I wonder if it would be terribly difficult to graft animations from one skeleton to another... Hmm...