I feel like boss kills would work best because unlike mana monsters, they don’t break sometimes and are consistent. They always come at the same time and anyone can be a part of them. It would allow for players to more easily plan for prestige instead of just hoping for the best.
I must say, I love all of these changes. I think that they will really improve the play experience of Earth. Now all we need is Geometry Dash 2.2 release date and we are all set for the new year!