Very interesting idea, but implementation can be better.
I think it will be better if you can switch to the ship's system just by using it, i.e.
- press WASD to start moving, but while moving, cannot start another system
- press space to start shielding
- press shift to recharge
- hold mouse button to shoot
and while holding any of the above buttons, disallow pressing any other buttons.
This can eliminate the use of number buttons, and still creates the dilemmas i am facing