a few minor changes i'd make:
first, i'd allow all layers to actually start with their gimmick. it really sucks that 1/10 level ups have to be used to unlock each character's gimmick every run.
second, i'd lock the availability of all level up perks that depend on another mechanics till the player actually has acquired that mechanic. it really sucks to have all three perks on a level relate to a mechanic you don't actually have.
third, i'd make opposing monster traits to be mutually exclusive. no more "don't fuck me too hard!" in conjunction with "i like it slow." in addition, no more blocking both methods with "don't fuck me too hard" and "don't fuck me too fast" at the same time.
fourth, i'd regenerate monsters if all three choices were too similar in traits. when all three choices are practically the same, there's no real choice.
fifth, i'd tie monster voices to genitals rather than chest.
sixth, i'd add in controls for species, color, and sizes. similar to what we already have for chest and genitals.
not so minor changes:
the dragon. in the higher difficulties, beating the dragon is extremely dependent on upgrade RNG. if you cannot get an overpowered offensive build going on, you need to have most of the stamina tree purchased.
in addition, on endless, i'd like to see dragon variants. at least when it comes to colors and sizes. i don't mind round 10 always being a red dragon with everything "huge," but on loop it'd be interesting to see variants.