Thank you for this question and for your patience in awaiting a response. I have given this some thought and investigation, and concluded that it would be quite a bit of work to add these features to MLA. I will consider this for some future release, but it may be some time before anything comes of it. In the interim, here is another plugin that may give you what you need:
User Access Manager
User Access Manager - NextGEN Gallery Extension
You could also look at the successor to Role Scoper:
If you investigate these and they do not meet your needs, I would be interested in knowing where they fall short.
Thanks for your interest in MLA and for this question. I regret that I don't have a more positive answer for you at this time.