sorry by the delay these days but I'm finishing some teaching tasks this week (exams, evaluation...). Anyway "the partial backup" function is in my TODO list (it's really huge ) and I'll start working on it as soon as possible (after prioritize the list), sure!
First of all, I've to do some important changes in the activities backup-core to support individual activities. After that I suppose that I'll start with a simple frontend (http://moodle.org/mod/forum/discuss.php?d=3964#17789). When everything will be working, we'll can do tons of interface refinements, isn't it?