Ok now I understand what you mean.
I guess Protection 6+ or Looting 4 or so could work but would it change much... Sure with Looting 4 you'd get better changes of say certain drops instead of all or just higher chance than 3 to make it interesting. But how to make it different so it enforces you to use it over commands (if likely) would be a challenge. So people that use commands don't prefer 99 or so when 4 might be 99 instead or something.
That or not just allows 4 & 4 for make protection 5 and 6 and so on, unless you mean that. Which could work but would be tedious and would need more with maybe challenges or recipes not just enchantments combined all the time I guess to make it interesting.