The project still ongoing, having received my adapter G36/M4 last Friday, I finally got to work on it.
So it's pretty simple, I cut all the dead volume of the room, once adapted to piston charger, you get this:

I also ordered last month a prototyping PCB for Arduino Uno to put all the electronics:

I'm still missing the charger that is being delivered, I will have to receive Wednesday to Thursday.
So soon find it for shooting video with a real supply of ammunition!