At the start of the match both tank players pick one hero
The 2 chosen tanks (or 1 if you picked the same tank) are the only ones that are allowed to be played for the rest of the match, all others are disabled
So if you picked rein and they picked orisa, you can avoid being trampled on by swapping to orisa and having a fair mirror match, but you can’t swap to say zarya to melt down the orisa.
There can’t be any more leeway than this. Since as long as there are at least 3 tanks you are allowed to swap between, there is a high likely for one of the infinite swapping cycles that make tank unplayable to be present (e.g. D.va → zarya → rein → d.va → …).
Dps and support counterswapping would still cause some problems, but isn’t nearly as problematic, so I don’t think this system would need to be implemented for those roles.
Perhaps you could get an opportunity to swap inbetween rounds in round based modes, but that could also lead to some annoying mindgames, so I’m not sure if it’d be for the better
And for the clowns who defend counterspamming on the basis of it requiring “skill”, you can’t complain about this solution, because it would be the highest skill version of tank ever. There is around a 50% chance (slightly lower because of even matchups) that the enemy picks a tank which wins in a matchup against yours, in which case you have to be as skilled at that arbitrary tank as the person who willingly chose to play it to have a higher chance of winning
Now there are better solutions to counterwatch, this is just, as the title says, the simplest one. A system where you can ban the hardcounters before they’re even picked could work, but there’d be a lot of kinks to figure out with that one. Of course the ultimate solution would be to just balance the game to the bare minimum extent that there are no forced to swap tank matchups anymore, but considering we’re nearly a year and a half into Overwatch 2 and they haven’t even made one balance change that attempted to do this for any of the problematic matchups, that does not seem likely