When you can't use ORM and have to have a rock solid and consistent business logic in database why not using the power of Python as part of database?
Using functions and triggers and PostgreSQL magic with plpy.
When we talk about free but advanced database engines we say PostgreSQL, right :) Imagine that you have to put a lot of business logic in database because the nature of you system stops you from using natural choice if we're talking about DB interactions - ORM.
How about using the whole power of Python and its modules with procedural programming for PostgreSQL. Why not creating some magic with PostgreSQL and Python? How about returning dynamic data tables results?
If you're not scared of learning some different concepts of database interactions or always wanted to learn some plpy tricks come and check what I want to show. Horizontal scaling and Python inside of PostgreSQL in easy way.