I think it would be silly to mess with any weapon's magazine size. If anything, a slight nerf to recoil makes the most sense. I honestly feel like there's enough recoil as is.
Lowering the damage while increasing the rate of fire would make the MP7 and Vector K10 redundant and more useless than they are currently. If you lower the damage without increasing the rate of fire, then it's the Peacekeeper with a much larger magazine. I think recoil is the only thing that can be tweaked while retaining balance.
There's nothing wrong with the PDW. The PDW and MSMC are balanced weapons by all means. It is 3arcs ineptitude at map making that exacerbates the strengths of the SMGs. If you really want to **** with MSMC and PDW users, grab a QBB slap on Stock Quickdraw and Laser and you will beast all over them.
"I loved throwing cans of flatulance at people sitting in corners. Even the hitmarker noise sounded like a fart. I will also miss those days." -aj4x94