No running with big guns? I'm sure that you even didn't think about it for 5 minutes, but ok.
I was once playing sniper with sharpshooter perk, and that's how I would deal with every biggunner out there if running with big guns was disabled in the game:
1. Catch him on approximately 50 hexes (range of sniper rifle).
2. Shoot in the head - check if he got stunned.
3. If not, just run a bit further to still have range advantage on him (so, about 50 hexes of distance)
4. Repeat 2-3 till he's dead.
100% safe and guaranteed to take out any big gunner.
Do you still think it is a good idea? Lol.
People, all you need to start is thinking about all consequences of something introduced into the game, not just "implement it because it sounds fun".Big guns are superior to small guns in close quarter battles but that's how it is supposed to be. Don't expect to win versus a big gunner if you try to "snipe" him from 10 hexes and obviously, that's how many people are playing their small gunners. Then they die and blame overpowered big guns for everything.
Now if you introduce no running or 9 ST needed to carry a big gun, hardly anyone will use it, so the next topic would be like "Nerf energy weapons because they are too powerful" and so on.
Small guns have to be improved, yes, just look at all those shotguns - they are totally useless in PvP combat, even those supposed to be powerful (for example Pancor Jackhammer).
Speaking about Strength requirements, there is already a difference between 5 ST sniper (or even 4 ST for P90) and 7 ST minigunner, but you just seem to haven't noticed it yet. Also, crafting ammo for a biggunner is one big mess - now think about all those who use small guns, how much ammo they need?
Before wipe and playing as a sniper, I needed at most 40-50 ammo for a major, long battle, if you want to fight that long with a minigunner, you have to bring more than 700-1000 ammo (that's how much of ammo some of our biggunners used in some of recent battles).
What about shooting from big guns? If you don't remember about splash damage, you will likely kill your friends. With a small gun you don't have to worry about that, you can take a good position and shoot from there and not care if someone is between you and your target.
Big guns were nerfed before, now since last wipe BROF is not longer working, so now what? Make minigun shooting 5-round bursts because you can't counter it with your hunting rifle? No, you just need to think for a moment to realise that with a smallgunner you have likely better perception and range than a biggunner and how to use it to win in combat.
If you need to improve or balance something, then waste more than 5 minutes on your ideas, not just "nerf X because I'm using Y".