The big(gest will) come/cum

WARNING THIS STORY-IDEA IS A CLOP-FIC

Heat-Season is coming in one moth, after a plague that almost killed all the ponies off, and now they need to repopulate, but they need to find a way to have all the stallions have-sex/buck all the mares, but none of the ponies have the time nor the energy to have-sex/buck with all of the ponies of the other gender in the time-spend of the Heat-Season. So all of the Princesses, (and maybe with the help of the mane-6, and/or Zecora) makes a spell to fuse all the mares together and all the stallion together for one day and have them have-sex/buck the other. When they un-fuse all the mares will be pregnant with a child from each stallion

4989971
Massively, I don't think it would work, but I would believe the concept to be interesting given smaller groups. Consider something like a sickness that had specifically killed or neutered stallions, thus making necessary to fuse large number of mares per stallion.

4990214 MHm... ok

p.s. the plague is jest a MacGuffins for why they are doing that