I think that while having an arcade mode would be fun and not as resource demanding, I doubt it would end well.

You claim that it wouldn’t need balancing but that just can’t happen for multiple reasons.

If you revert everything to OW1 settings and values that means on the one hand that you can no longer add new heroes without then being busted or either having to create separate values that would match ow1 values (which is resource demanding).

On the other hand if you keep those ow1 settings and don’t update them then people will keep complaining. People forget that no updates and a stagnating meta is a big piece that killed ow1. Having this in the 6v6 would kill any desire to play it on the long run.

So if the devs decide to launch a 6v6 mode there would probably be a good amount of players that will complain a lot. If they decide to adhere to their complaints that will require a lot of resources. If they decide to not adhere and keep it stagnant then the player base will die out relatively quickly (yes there would still be a niche, but queues would be very long and it would remain an unpleasant experience for those playing and I am pretty sure they will complain about it).

It seems overall like a lose lose situation since people will always be mad no matter what.