Karthus Ultimate Changes

So i was watching a video of Karthus and two changes for his ultimate has came to my mind. The first is that you shouldn't be able to press R when all of the enemies are dead. The ability's icon could be grayed out when this happens. The other is something like Cho or Zed has: an indicator which shows when an enemy is going to die from your ultimate. It would really help Karthus to manage his ultimate usage since its on a reaaaaaaly long cooldown(for obvious reasons tho). I think theese wouldn't broke him or anything but they are some neat quality of life changes.