While this topic has been talked about before, I figured I'd give my two cents on how it would work.
First as to how to make a musical with humans and anthropomorphic animals work, I think the humans would wear normal cloths, while the animals would wear customs shirts that would give the actors the look of an animal. Something like this.
As for songwriters and composers, well here's a list of some people that I think could do a good job in writing the songs.
1. Stephen Schwartz (Godspell, Pippin, Wicked)
2. Robert Lopez (Avenue Q, Book of Mormon, Frozen)
3. Lynn Ahrens and Stephen Flaherty (Once on This Island, Ragtime, Seussical)
4. Karey and Wayne Kirkpatrick (Something Rotten)
What do you guys think?