Point is that they didn't need to be changed in the first place. A merc buff leads back to 1.0 matches, which we all can agree no one would like. You already nerf the gat by nerfing heavy ammo, so roll with gatling unchanged and try that.
This is my opinion, but mercs and gats are fairly balanced right now. People want more options but that requires more guns which as you say, isnt going to happen now, so thats how that works.
The issue with nerfing heavy clip is then you indirectly nerf any gun that can successfully use it. Sure you get gat in there, but you also grab carronades and hwacha, which don't need nerfing (opinion). So you look at the gat itself. Maybe a small clip size nerf? Then greased will look nicer for its increased clip size, or you go for more precise fire at the cost of lower dps.
Mercs also don't need penetration. It's cool and all, but I just had to face against 5 of them pointed at me last tournament, and god forbid if they were knocking out multiple components with one shot. You would have to nerf it so hard, that it would lose its purpose to begin with, so I'm not for that.
We all appreciate the work you and Muse do for us.