[brutimus]

In any situation like this I've been in and tried to attempt django, it's turned out to be a complete failure. You need an ORM that knows how to construct SQL properly and map existing tables. Go with your second option: SQLAlchemy. Use that with SQLSoup (an extension), mapping tables on the fly is a breeze and you can manually tweak your queries to do about anything you need: polymorphism, correlated subqueries, etc. I have a feeling that if you attempt the Django route, you're going to spend more time wondering "well why the hell doesn't this ORM do _____?" That's my opinion on the subject.