azarunPPhoenix21
Soldier's banners fall in your criteria too, but they are both viable and balanced.
Lets face it valve will never remove sandman from the game or make it a stock reskin. Might be better nerfing them to the point where high level players would prefer consistent stock over gimmicky unlock.
The difference is that soldiers are giving up either reliable hitscan or 20 hp rocket jumps while everyone else is giving up some shitty secondary that they'll never use.
When you run a banner, there'll be times you miss the reliable shotgun hitscan or cheap jumps, whereas when are you EVER going to miss a shotgun on heavy, who has a primary that is so much better and never needs to reload.
The only weapon I see that might be missed is pistol, and that doesn't matter when mad milk,crit a cola, etc are so OP