One area that I am continually wanting is some fine grained access into branch management. For instance our workflow consists of a developer creating a branch from master and pushing the topic, bug or feature branch upstream. When we go to release to each different environment we have specialty branches (develop, qa and master) which only a few people should have write access to but anyone can read.
I would like to see some finer grained permissions on who can utilize these different branches to prevent unauthorized writes. What we currently do is manage this in github and we have them issue pull requests then merge the topic branches upstream. Following that we merge them into the specialty branches since they do not have permissions to the upstream repository.