I don't think nerfing is needed. What I do think is needed are players who can implement strategies that neutralize stronger weapons (and the sniper rifle-scope-prone-switch glitch needs to be fixed). Every CoD game has had stronger and weaker weapons, and not every higher-level weapon, perk, equipment, and/or attachment is more powerful than the one you earned before it. The Famas from Black Ops or the AK-47 from Reflex are great examples. It's up to the players to decide what weapons to use by learning the weapons' strengths and weaknesses and setting up your classes to match your playing style.
Also, if you tell me that Akimbo FMG9s have no weaknesses, I disagree. FMG9s CAN hit you across the map but CAN'T kill you in a single burst because of the recoil - assuming a player is playing legitimately and not SR glitching. Even Steady Aim/Pro can't fix that. So fight Akimbo FMG9 users with ARs or SRs. If you prefer a closer fight, use shotguns with extended mags, scavenger, and steady aim. Or, just use Akimbo FMG9s against them.
I have one class with Akimbo FMG9s to fight fire with fire. Another class I have an MP9 with RDS for medium-range pick-offs. A third class has Overkill Pro on it, so I can use an SMG for up-close fighting and an AR with a hybrid scope and stability/breath for longer pick-offs. My other two classes are set up with Akimbo MP9s. They're not as powerful as FMG9s, but you don't have that stupid animation when first switching to them, and they have less recoil than the FMG9s. It's all how you play.
If you are really an Akimbo FMG9 hater, you really only have a few choices:
1. Play with "fire fighting fire" (use Akimbo FMG9s or shotguns with ExMags)
2. Play with weapons you like and deal with other people using FMG9s, etc.
3. Play the single player campaign so you don't deal with Akimbo FMG9s
4. Play spec ops survival so you don't deal with Akimbo FMG9s
5. Play something other than MW3 - but we'll miss you
