I think the guns are mostly fine, SMG's could do a little less damage over long range, and the two semiauto shotties could use a bit more range but other than that i don't see any huge issues and can live without any changes. The Remington got a nerf it didn't need, but it's still quite good. I've gotten mastery on all LMG's, snipers, SMG's, shotties, and still have 4 AR's to go so i've played with most weapons quite a lot. In my opinion the weapon balance overall is better in BO2 than in other CoD games i've played.
The one nerf this game needs is adding visual recoil to the target finder scope so that it matches the weapon it's used on and actually relates to the magnification level, now it seems to completely take away the visual recoil which makes it too easy to shoot to long distances with it. And there should be some more flinch when you shoot a TF user, now it seems they stay on target even without toughness which is also a too great of a benefit.
M27 - No, it's just fine. As mentioned, like the Commando, it's meant to trade off power for being more accurate. If you add more damage to make it both very accurate AND powerful, that just makes it OP in the end.
SWAT - Why? With a "2-shot kill", you're shooting someone with SIX rounds which is more than enough to kill, even at a distance, with it. (Only takes up to 5 rounds with ARs at long range usually.) Reduced recoil with Select Fire...the recoil was INCREASED with the patch because people thought it was too accurate with Select Fire. Slightly increased recoil, like there SHOULD be with ANY burst fire weapon suddenly being fired full auto, helps keep balance.
Type 25 - Again, it's about trade-off to make the weapon balanced. The Type 25 has a high rate of fire with only moderate, but controllable, recoil. Adding more damage and/or more rounds pushes it into OP territory because you'd either be able to easily kill a person at virtually any range and/or you could just "endlessly" spray a person and, coupled with the high rate of fire, that person would have virtually no chance of escaping or fighting back. This is why the PDW-57 may have a high capacity magazine and a bit of power (up close, of course) on its side, but also a much slower rate of fire than other SMGs to counterbalance it.
M8A1 - Same thing as the SWAT, only this time, you're putting 4-8 bullets into people AND its damage along with recoil with Select Fire was slightly decreased with the patch because it was too strong otherwise. It still works just fine to me from my experience, still getting 1 burst kills from decent distances.
Skorpion - Are you kidding me? Do you realize how OP the Skorpion would be if they did that?
Vector - As said, reduced recoil is the whole point of the Vector, but it's still slightly less than things like the PDW-57 in terms of power. It's just fine the way it is, pretty much in the middle of the SMGs.
SVU - Also the point of the SVU. Unlike other snipers, which can usually kill with just 1 shot, the SVU will usually take 2 to kill unless you can get headshots virtually every time. If it had too much recoil, it'd become pretty much useless in any capacity.
XPR- Same as the SVU.
Are you REALLY thinking about the game community as a WHOLE with your list or are you, more likely, like many other buff/nerd "suggestions" I see on these forums, just listing off things YOU want to happen to make it easier for YOU because you aren't able to use these weapons like lasers at every range and don't want to be bothered taking the time to get used to them and master them like other players, while those that kill you "easily", like always, are seen as "too good"?