Not that necessary since it's called as "Freeplay" , however you could probably add +3 , 4 , 5 Success Celestial Items Recieved every +5 /+10 Prestiges after P5 or any other benefits that would be fair for everyone , Rank kit level 13 etc.
Only a suggestion since it's still through hard work after p5 it would give a little bit of reason to mine beyond freeplay