They could already aim for a more complex system that would enable infinitly (well, almost) many weapons.
I think a Mechwarrior-esque system could handle it very well - especially if some mod decides to use Gunboats or just use plainly a lot of guns.
We could use the numbers 0...9 for selecting weapon groups.
Shift - number would assign a weapon to that weapon group.
4 more buttons/combos should be reserved for - selecting next/previous weapon and next/previous weapon group.
Beside weapon groups firing modes could be implemented too:
This would require a recharge rate set for weapons - the difference would be that instead a set ROF, each bank would have a ROF set on their own.
-Group fire - all the weapons in the group fire at once - the current linked fire
-Chain fire - the first weapon in the group fires, than the next, than the following one and so on it wraps around the group.
It can be a lot faster than group fire, since the faster gun doesn't have to wait for the slower ones while they recharge.
However this means only 1 bank fires at once, and it consumes a lot more energy.
-Mass fire - all the weapons fire in the group indepently as fast as they can.
The firing mode with the greatest ROF.
The most energy consuming too.
The last may be reserved for MODs that allow it, since there should be some drawback to change the canon firing (chain fire doens't break it, you coul already do that by continously switching banks).
Maybe heat management, or additional power drain would make it balanced enough for gamplay.
