Hi Piquet!
First of all, it seems to me that you'll be able to solve your 10 week task as long as the actual application doesn't take longer than that to wrap up... ;)
There's no relations between users and members, but you could create one of each with the same login and password and try to find a way to pass them on the frontend. I'm quite sure there is an acceptable solution to this...
Regarding your roles, many of them could probably be assigned as member groups for the frontend application, but for the backend this will not be super-easy if you want complex access rules on a group of users. For individuals this is implemented allready.
The applications I've worked with has taken care of the access logic (below page level) themselves an just picked up the member loginname and group/s from Umbraco.
// ;) Kalle
" - Yeah I'd like to share your point of view, as long as it's my view too... (
http://www.d-a-d.dk/lyrics/pointofview)