A few other points.
1.) Give server admins options built into the game. Tracers on or off? Run with the 32 player weapon loadout or the 50 player one, regardless of map size? When you're basing a game off of the Unreal Engine (whichever version), the whole idea is about versatility and customization. If you accept that mutators are fine, why not include those same sorts of options as a choice for server admins? If the fear is "But what if people think the modified game is actually the core game and they base their opinions off of that?" then the response is "Well, if they can already run mutators, how is the risk any different?"
2.) Figure out your gameplan as far as your target audience and stick to that gameplan. Do you want to broaden the game's appeal to people who weren't otherwise interested in RO? Do you want to keep the core audience? My advice is that you NOT make changes to the gameplay (aside from, say, improving existing systems to function)
For example, when RO:Ost first came out, the tank code wasn't working properly, so angling basically didn't do squat and all tanks died in two hits. After the first (or second?) big patch, tanks were able to withstand more hits (although they still mostly die in 2, but that's a side issue). That's an example of IMPROVING existing functionality. You never intended that tanks would be all dying in 2 hits, so the change was more like a bug fix.
By contrast, changing the number of full-auto/semi-auto/special classes on 50 player maps vs. 32 player maps (and not leaving servers an option to revert to 32 player loadouts), that was a change to gameplay that was perhaps more fundamental than realized at first. It certainly can change the PACE of gameplay by not limiting people to using the bolt. With your core audience (the guys who came here from the mod days), that's not an issue. Bolt, semi, SMG, doesn't matter. They're fine with whatever and some prefer the bolt even. With the newer players and folks from other faster-paced games, the idea may have been "Well, they'll want to use weapons that let them get into close quarters fighting quicker, and we don't want to limit their options or they'll ditch RO."
The problem here is that you have to sort of guage the identity of the game itself and figure out what your audience wants. Duh, right? But easier said than done. Personally, I think that you can gain a wider audience by adjusting certain aspects of the game, while maintaining the other core aspects.
I tend to think that things like changing weapon loadouts deviates too much from the core, but at the same time, enough of the core remains that changing weapon loadouts alone won't win you any converts. So in the end, you change the game that way and actually take a net loss.
Other things can be done, however, to make the game more accessible to players. A training course for single player would help, probably (IE: including a firing range and tank range map). More fluid animations probably would help too, as well as adjusting the speed of the avatars some. Right now, RO avatars move at a rather slow default speed (even slower if you go to iron sights). Their sprint, however, is considerably faster. By comparison, BF2 avatars move pretty fast all the time and sprint even faster. I'm not saying you should up the speed to BF2 levels, but you could reduce the difference between RO's movement speeds and thereby make the game feel differently paced, even if the net effect is that everything remains basically the same.
Like I said, I also think you can gain a much wider audience by includng more theaters. I know a lot of people who play Forgotten Hope -- to this day -- who aren't interested in RO because it doesn't have North Africa, Western Europe, or the Pacific. I know it's a ton of extra work, but I do think it'd make the game more accessible. I recognize that the eastern front is the primary focus of the game, but while the gameplay is fantastic, I think that this ends up keeping more people away than necessary. They'd love the game mechanics, but for whatever goofy reason, they can't handle ONLY playing one front. As we've also seen, saying "Well, the mods can develop that content" only takes you so far because, while I really look forward to them, it's now almost, what, 2 years on and we still don't have any full-fledged mods for RO.
It's adjustments like that that I think could do more to capture a wider audience while still appealing to your core audience. Changing the gameplay itself, though (as opposed to fixing it to work as it was always intended to), even subtly (IE: adding more semis/SMGs to 50 player servers) may cause more harm than good. Especially after you've already released the game and people have gotten used to it as-is.