We did this the other day and it was pretty fun. We shouldnt have to be 12 of us in 3 premade groups queuing at the same time and coordinating the ready checks in discord to all end up fighting each other.
I don't think anyone would complain if such a custom lobby didn't give any rewards. If anything, incentivize queuing for randoms by giving gold jewelry from random non-BG sets a nano chance to drop.