Please don't change Swain's ultimate. He's one of the last remaining magic drain tanks in the game.
All of Swain's kit aside from his ultimate can be changed without really ruining Swain's identity or gameplay, but his ultimate cannot be dramatically changed without completely alienating his playerbase unless it keeps the healing. Swain isn't bursty, he doesn't have a ton of utility, his kit relies entirely on his ultimate.
Vladimir was shifted from a drain-tank into a weird protobelt burst mage, so please, let Swain remain a drain-tank. New Morgana is cool but got hotfix nerfed hard and her sustain isn't really similar to old Vlad or Swain.