My perfect vision would be that the fighter and rogue are redone to have the same supernatural possibilities as monks or blood hunters. The magic is baked into the base class. You are capable of supernatural stuff from low level. Your subclass could define the type of power you have (arcane, rune, psionics, primal, shadow). The idea of a pure "mundane" fighter or rogue is gone, but in its place are classes that can keep pace with what wizards and other casters can do. A rogue who can go invisible or teleport in shadows. A fighter that can fly/jump great leaps and wrestle with dragons. Not spells or spellcasting, but supernatural class features baked in the base class, and can grow with the remaining 16 levels of the base class rather than introducing them at odd intervals.