Basicly it is theoretically possible what you wish and I also had an idea in that kind.
But after testing with Tobii now for few days I realized that this is not good enough to do but it possible of course!
The accuracy is mighty but still for Gaming it requires a huge amount of accuracy which Tobii does need and does not have right now atm!
The commands take minimum 1 second!
For gaming this is too much. Genuine mouse commands with hand need less than 100 ms!
So to be clear: This is NOT flexible nor “pleasant”!
Actually you have to programm for every game a special Overlay. Most FPS are luckily the same so there is not much work to do. Maybe you can do a Button remap for this special TOBII GAMING HUD yourself. But you would need profiles for every own game. 😉