I'll say I find the distinction between "rifles" and "carbines" to be pretty bad. Both are "Rifles" when it comes to proficiency and then presumably everything else. Both deal the exact same damage with the exact same number of shots. Then you get to the differences where the rifle can attempt shots at 151-300 squares (how often have you ever seen those in a game?) but good luck hitting at -10 while the Carbine gets to weigh half as much, costs less, and gets to make AoO without even folding the stock.
Well, I'm not sure what point you are trying to make here. That carbines are a bit too good at everything? Sure, I'll bite. I even agree that unless you want to use a lot of autofire, you should probably carry a carbine. Slap on a 100 credit scope on said carbine, and even those 200 m pot shots should be easy enough. It's easily one of the best weapons in the game, maybe even too good.
So, if you have a carbine or a rifle you should try to place a sniper that can control the field as often as possible, even as a player. If the GM never let you do so, I can't help you with that. Every time you have a meeting with some shady character, you should try to scout the place out discreetly and place a sniper or even two. If you do, they will like those scopes an the Far Shot feats.
Now if you're worried about the status of Pistols in the game I'd just say that in so many ways the Blaster Carbine already takes them over. I mean you the folded stock on them and you'll get the idea that you can wield them just like you would a heavy blaster pistol except it's a little heavier, cost more but is easier to acquire, and it has autofire as an option; if a target gets out to 61 squares could just extend the stock and use it with rifle ranges and be no worse off that if you firing a pistol at those ranges.
So once again, maybe the carbine is a bit too good? They are lighter so a little easier than rifles to handle I guess, but maybe they should get the same treatment as rifles as far as making AoOs? Still don't see this as a reason to make pistols worse.
The way I see things, I think that a Blaster Pistol is supposed to be the prefered weapon to make an AoO! To take that possibility away makes little sense to me. But if you do, there is going to be more than one talent or feat that is affected. Opportunistic Strike from the Run and Gun tree is one that will be less useful I imagine.
Now the proposed change is a house rule, so it is optional. If you want to play your games like that, there is little that I can say to stop you. If it is up front announced as a house rule, every player has the choice to accept or choose a different game. As long as he's not playing a Gunslinger that focus on AoOs he would have little reason to complain!