Idea for 6*
Introduce brand new champions that are only available as 6*. One of the biggest drags is spending all your resources on, say, 5* 4/55 SL or Magik and then find out there will be a 6* equivalent some day.
Release new champs that are only 6*. So that a 4/55 SL, etc is still special and useful in the game. Prevents having teams of 5 hulks or collosus's of different star levels, and makes us feel less bad about sinking resources into our 4 and 5 star champs. If that mean fewer 6* total for a while I'm ok with it.