I would prefer that it has a fixed “set” of mutators to use in every Brutal+.
For an example: You will always get Just Die + Barrier OR Barrier + Leech + Tornado OR Transmute + Speed Freak and so on every time you play Brutal +
And at Brutal+6 you will get a fixed “set of 4 mutators” instead of “set of 4 random mutators”.