So I did some research on the topic, and I'll share what I learned.
With the django-nonrel app getting better, it looks like a lot of satchmo itself wouldn't need rewriting, but the dependencies probably wouldn't work right out of the box. If you weren't going to use django-nonrel, then any model related code (it's obviously a lot) needs to be completely rewritten. I started doing some of it, then I just gave up because it didn't really make sense.
I'm partially speculating here because I don't know all the rules, but I don't think the app engine is PCI compliant. That being said, you could still use paypal/google checkout.
After all is said and done though, I don't think there's anyway to get around the reportlab dependency, and you'd probably have to write something to use google's image library, which I don't think would be anything short of a real pain.
My guess is: it could, but would take a lot re-writing, and would not
be very practical.
--
Brian O'Connor