Is there any way to, for lack of a better word, "un-upgrade" moves?
I grabbed Circe's Bash upgrade early on, and discovered that this was a really poor decision, because the "upgraded" version has a strict Aggression requirement, so she has no moves I can always use... and her special move to max-out Focus doesn't help, either, because I noticed and bought it AFTER picking the Aggression-based upgrade. She'd previously been a favorite haremon, and I ended up benching her entirely.
History repeated itself for Vex, except worse, because her Jab was an always available attack that did a lot of damage to a single-target, and turned into a very tightly restricted area-of-effect that did okay damage to every target. Not only was it no longer accessible, it was a completely different move with a completely different role.
Same goes for all other upgrades - Hiss actually saw much less use than Purr, because Purr was always available and the slow drip-off of debuffs means I wasn't often spreading damage around anyway.
There's a lot to love about this combat system, but pricing myself out of actual functioning moves really isn't a good feeling. I ended up teaching everyone Takedown by seducing condoms, just so I had a last-ditch damage move like a Magikarp that's run out of splash. Vex should retain Jab even after I grab Hades Spear, or just execute Hades Spear when I Jab past a certain level of aggression. Same goes for similar upgrades.