You said its not possible for technical reasons. However with OW2 you got the opportunity to optimize for a higher player count.
Having a 2-3-2 format with triple dps would not only improve queue times, you wouldnt have to brake tank synergy and you would have more space to buff tanks into feeling OP because they need to absorb more incoming damage. Would also improve meta variety as there is now more space for a more unconvential option.
5v5 would suck, because you brake tank synergy and you could easily end up in a situation where there is that 1 tank which is clearly the best at all situations, which could mean a balancing nightmare.
Especially if you rework them all into being brawlers and they are all just mainly focused on offense. The one who get picks the easiest way will be picked all the time.
I actually do strongly, but I think if there were any chance of it we would have gotten a hint with Blizzconline, but there is none. I think its the single best answer for many issues including DPS queue times with a role structure. I just think its telling that the OW team was so … lazy? That they didn’t see the wisdom in an entirely new engine to support it, with reworks to the maps and so on.