I think a great combo would've been Django's features, packaging and most importantly documentation, but with SQLAlchemy and Jinja2 technologies underneath.
The nice thing about Django is that there's nothing stopping you from doing that. You'll have to give up the Django Admin if you use SQLAlchemy for models but you can still do it. I have several projects that use Elasticsearch as a backend and one that's based on JSON documents in Git repositories. You can totally do it!
That would have been hard since both of those projects came out after Django, but just an FYI Jinja2 templates are supported and nothing stops you from using SQLAlchemy. Granted you lose a lot of the tight intergration that makes Django great to use.
