Balance balance balance. When the whole game becomes one big numbers juggling act, the result is homogenized garbage.
Bring on the huge weapons! Even though I don't currently have a ship that could ever put them properly to use, I'd love to see them in the game. You just need to think of non-numbers ways to make things interesting, instead of flat upgrades.
For example, huge railguns could actually increase power draw on your reactor as you charge them, meaning that trying to fire a pair all at once would be a gamble. Modules should have to shut down and reboot unless you fire them one at a time. Thruster response should be decreased while charging them, due to reactor spiking, further complicating aiming and requiring even more skill from the user.
A huge frag cannon might push you around from the recoil, for example - like taking an impulse-based hit.
Just random brainstorming. There are ways other than sheer numbers to make heavy-hitting ordnance more difficult - and therefore more interesting and rewarding - to use. Just saying such weapons flat out shouldn't be in the game is a boring concession.