What if we do such an experimental mode and see how it goes?
No repicks, you pick a hero before match starts. 2-2-2 stays. If you are alone MM matches you with a corresponding setup. If you are in a group - cooperate what to pick. Only 1 shield tank is allowed (Sigma or Rein or Orissa). (Winston is not a shield tank) SR for every hero. Calibration - 3-5 matches should be enough I think.
Why I think no repicks is important and will prove interesting:
1st - this will provoke players to match up with friends or other players more than in the past. Because this will help to make a more universal team, because you can’t repick. So thinking enemy team, same as your team will have only 1 shield tank and 2 DDs, you need maybe 1 hitscan, 1 projectile, 2 heals 1 shield tank and 1 non-shield tank.
2nd - The fact that enemy team has lets say a strong widow, and you pick tracer or genji to take her off, does not make you a better player, its just you picked a counter for that other strong player, so after he dies 1-2 times he will take Mcrree to take you down. This turns OW into a repick game, not a shooter game. What I think is wrong.
I think this will kill the shield meta, and make most of heroes playable again, and bring back fun hopefully.
I hope you like this AT LEAST AS AN EXPERIMENT (or suggest edits/improvements) and please upvote so papa 
and other devs can see this and think it over.