It might not be hard to do, but it is time consuming. I mean, currently we have, what 5 factions (player, Hegemony, TriTach, Independent, Pirate), at least? So that would mean at least 10 different sprites for each weapon added (hardpoint & turret, just in case there's any confusion, although I doubt there was). For adding a new faction to the game or mod, there's 66 weapons (including missiles though) that would need to be redone in that faction's style, so that'd be 132 additional sprites needing done (again, hardpoint & turret).
I know that may look like I'm whitewashing your idea, but it isn't intentional, just pointing out the impracticality of it, although Vandala has indirectly stated that the whole thing could be an optional variable. Like I said before, I do like the idea, just not the monumental work that'd have to go in for mods/extra factions to be completely utilising the feature