I agree, an OtC All Bosses Speed Run would be very cool thing to try and optimize. The only issue is it will take a bit of grinding for players to unlock the entire map, but having just done so, I can definitely see the appeal.

I could see an interesting possibility space in different challenging versions like, where you have 1 weapon, no arcana, no eggs (which seems like a default here), specific characters, specific banishes. I feel like to make it the most accessible, it should focus on a small subset of characters, given how there are SO MANY to unlock/choose from in OtC.