As said, 3Dmax has many plugins, and has biped by default, it’s not buggy,
if you spend the time to learn it well, you can do a lot, not to mention you could use Maxscript, you don’t need python.
I don’t see any need for making a similar plugin for 3DMax. Maya is said to be best for animating anyway, so it’s a good idea to learn it,
once you know one 3D software it’s not as hard to learn another one, or just parts of it.