This game is too designed around counter swapping to lock it. Without reworking all the heroes this would not work well at all.
What I would like to see them try is hero timers though. Also Ult resets to ZERO.
This would stop people from tank swapping constantly.
So if you swap. The hero you were gets a lockout timer (for you). AND/or you cannot swap again for 1 minute.
They need to make swapping have a serious opportunity cost component to it.
Actually, maybe instead of timers which would annoy people. Make it cost 50 ult charge to swap. So it’s not just so arbitrary and brainless.