>>536950050
There are simply too many key levels.
>delete heroic and replace it with current +2 with timer and everything
>base mythic replaced with +4 tuning for affixes, champion gear, runed crests
>new +2 is current +7 for fort/tyranical and hero track/gilded
>new +3 is current +10 for myth vault
>new +4 is current +12 with the death penalty and myth track vendor
>+5 and above continue scaling for the mentally unwell pushers

The other keys may as well not exist. You could also just make +2 tuned like a +10 and have higher keys not give any rewards just like today.