In Tower 3.2 (just released about a week ago), there is now the ability to specify inventory from source instead of having to define it using either the UI or API. See http://docs.ansible.com/ansible-tower/latest/html/userguide/... for more information on this. Hope this helps!
You hook AWX up to git or similar. It will pull playbooks, etc, from git before execution. I was a Tower sceptic at first, but it's actually really great.
I'm guessing AWX wants to be the central "source of truth" for all of that stuff instead of just keeping it all in a single git repo.