I'm working on a project that also usen quite heavy 2D graphics AND a camera..
( also openCV) Would it be possible to get a camera frame on an allegro bitmap ?
If so allegro 5 would be a candidate for the whole 2D stuff..

Yes!

I have a class in AllegroFlare (only depends on allegro5 and openCV):

https://github.com/MarkOates/allegro_flare/blob/master/examples/opencv/cam_view.h
https://github.com/MarkOates/allegro_flare/blob/master/examples/opencv/cam_view.cpp

now we have a video playback plugin for allegro, maybe a video capture plugin could be nice...

I would just link it with OpenCV (make it easy to use both together / OpenCV's data structs) than re-invent the wheel. It's already a super well-known library with tons of programmers and schools supporting it.

WARNING: IIRC, old OpenCV is C (which Python has bindings for), but the new OpenCV is C++ and heavily uses templates to make everything prettier so there's much fewer binding support for say, Python. They said the older OpenCV (2?) still works fine, but the new one was refactored to model "where the industry is moving" in terms of hardware.

Opencv is a bit of a beast, i think we could make something smaller and lighter ourselves, directly on theos specific api. Or maybe use a lighter video capture library.

Thanks a lot Mark
this is exactly what I was looking for