I had to spend some time to permit to a project of ours to use Elixir inside TG2. Maybe someone with more experience than me might have a better answer, but I have been able to make Elixir work this way:
First of all I had to make Elixir use my TG2 metadata and session by adding to each model file that has a class inheriting from elixir.Entity this line:
from project_name.model import metadata as __metadata__, DBSession as __session__
Then I had to switch to model __init__.py and add elixir.setup_all() to init_model function just after DBSession.configure. This is really important as makes Elixir create all the SQLAlchemy tables and without this you won’t see anything happen for your elixir based models.
Also we can now import inside your model scope every elixir.Entity inherited class like we usually do for DeclarativeBase children.