is there the possibility of making parts of bestials more customizable?
add new heads of animals and especially body parts, clothes and hats?
add animals as sidekicks, like Krypto and Ace?

I believe that all this can be implemented but there is demand for it?

A lot of that sounds more like it would be better off in the Suggestions forum, since there isn't really a lot they can do to make things more customizable that would technically fall under Combat/Powers.

It really looks more like costume work (which I support, mind you - some more options, especially in the 'claws' glove department would be great).