The tread on the fire extinguisher valve is a kind of a hybrid. Based on the BSP idea, 5/8 but with higher TPI.

Your setup needs a dump valve in between the FEV and the isolation ball valve.

For the rest, it's just heavier than most setups, but not unsafe.

I would fix the ball valve in the robot, and make the connection between bottle and that ball valve with a flexible hose.