I have myselft though in these ideas of having more than 2 fire buttons, but then I started to think about all the control options the game, and the most limited ones are the gamepads. And they are already overloaded with all the options, so how would your suggestion be to adapt this more fire button idea to the gamepads? As the gamepad is the main controller used by console players, it is quite an important that it works there too...
Also how would this work for the pc players, as I would expect quite few play with mouse and keyboard, so with a standard mouse, there is 2 buttons, so the other fire buttons have to be on the keyboard, that you already are occupied with flying...
So that only leaves the HOTAS players who depending on HOTAS have from to few buttons to too many buttons.
So how would this work for all the controller options in practice. I still like the idea, but unless we can give good arguments that this would work on all the most common controller setups then I doubt FDev will change any of their design decisions regarding this.
[edit]
obviously, you cannot have to many buttons...
I have a good arguement, there is no drawback from implementing it. If you can't assing more than 2 fire buttons because of hardware limitations and your fire groups are working fine than you wouldn't need, but it is still there for those who CAN use it. So why not? Why not add more convenience to the game? It would be so simple.