For anyone interested, here are the current modifications we have on heavy for VSH.
Heavy
Killing Gloves of Boxing
Weapon disabled. Replaced with the Gloves of Running Urgently.
Fists of Steel
Weapon disabled. Replaced with Fists.
Gloves of Running Urgently
On active: faster movement speed. Increased damage vulnrability.
Holiday Punch
Removes any stun when hit by the boss.
All Miniguns
+15% damage boost when healed by a medic.
All Shotguns
Some damage returned as health.
about the warrior's spirit. The damage vulnerability being removed would be too big a buff imo. The extra damage is quite good, and not having a downside is difficult to justify imo.
The possibility of changing the crits to mini-crits for the buffalo steak is there, but I'm not sure about balance. I think it's possible to work with however, because taunting gives you some crits, and giving away your shotgun's healing for a damage utility might be good.
As far as I know, heavy is rather weak in VSH if he's on his own. When paired with an engineer or an organized team, he becomes significantly stronger. The main problem that I see is buffing the weapons that make heavy too powerful when he's at his best. The optimal way of balancing the weapons would be to buff his solo play without touching his teamwork-play.
I am by no means experienced in balancing weapons, just dropping my opinion on this.