I like both the Contribute and MyOmeka plugins and they would be excellent together. Both of course can be installed, but the need to register for one (MyOmeka) and then provide a name and E-Mail for the other might be a turn off for users.
Unless I'm missing something and this has already been done, I believe that would be a fantastic addition.
You're right, this doesn't exist.
More than even just supporting MyOmeka, Contribution should probably just detect if you're any kind of logged-in user and automatically pick up your name and email, and not ask for them.
Another possible course that we're looking at is basing things around the a Guest User plugin, which just does that job of providing a public-facing login. Doing what John says is a good plan, as always -- making Contribution detect whatever kind of logged-in user.
That sounds like a good solution. The project I'm working on was presented recently as part of a graduate thesis, and something along those lines was actually suggested by the members of the panel when they asked about the log in.