You can sort of maybe use SA with Django, except when all the apps you use depend on it and you have to use SA reflection to get at your data. Sadly, the integration is poor.
I totally agree about the regexes: only a small subset of all routes will ever need regexes, and you can do it explicitly in Flask when needed.
The part I really like about Flask is the decorators for routes. This is how it should be, not some messy file of reg-exes.