The Tavern

Confusion effect is often called tax for potions of curing but at least potion of curing has multiple effects: removing poisoned status, curing rot, some minor healing so there is still some choice and you often can see players saving the potions when there is no danger of dying.
Potion of cure mutations has just a single effect so it is much easier to use: if you have bad mutations, cure them. There is no any sense to save them, at least when you already have 3+ mutations. Making the potions more rare does not work, you still can have too many in some games and too few in other games and in both cases there are no interesting decisions.

I suggest to rename potion of might to potion of power and give it two effects:
1) current effect of potion of might
2) current effect of potion of cure mutations
The rename is necessary to avoid problem with old players losing all mutations unexpectedly, hopefully new potion name will make them read description to see what it does.
As side effect, it can help to make potion of might more interesting too, currently good players always quaff it vs orb of fire because it has very high AC. Probably some players will try to save the new potion to cure mutations after the fight and will die instead, other players will not have a way to cure the mutations because they quaffed all those potions earlier, both situations are arguably good.

While I understand the reasoning, I dislike the idea, as it would put an end to my stacking of good mutations. I don't want a buff that removes my other buffs... OK, I'll amend that: if the change does happen, remove the said potion from Gozag's Potion Petition, 'cause I don't wanna risk loosing all my mutations every time I use it. If I wanted a god of no mutation, I'd go Zin(after mutating myself, of course).

Potions of cure mutation are a bad feature, yes, but your specific suggestion is scroll of inversion-tier bizarre. Remove or change the effect, instead of trying to hide its problems by tying it to an unrelated less-problematic effect.

There is an idea I have which is only very partially formed, that of making malmutate disappear with the exception of shining eyes and instead making contamination much, much, much more frequent. Like, casting spells, being hit by spells, being in proximity of magical (undead, flying swords...) or mutagenic creatures, being near someone casting a spell, wielding branded weapons, all of these increase your contamination. The idea is that of making mutations a lot more frequent, and having all potions have a randomly powerful "cure mutation" effect, which would suddenly make potion of degeneration not that useless. No potions of mutation, good mutation or cure mutation, maybe throw in a "scroll of fix mutation" as rare as a scroll of branding, which you can use to make a mutation of your choice permanent.
(I don't expect this to be implemented, it seems very distant from the current direction).

Potion of Ambrosia was design to combine two shitty items (!oConfusion, Ambrosia) into something sometimes-useful. Merging !oMight with !oCureMut solves a problem that is nonexistent.

IMO just remove bad mutations and make the rest a mixed blessing (like it was done with amulets) instead of always-good muts and always-bad ones.

Alternatively, merge potions of Mutation, Cure Mutation, and Beneficial Mutation into a single "Potion of Mutability." Adds 1-5 random mutations (at least 1 good), removes 3-7 existing mutations. (Or whatever numbers seem appropriate). I buffed the "remove" side over the "add" so that removing malmutations is still realistically an option.

Makes it harder to keep yourself to only good mutations, but allows for guaranteed good mutations, random mutations, and removal of mutations. Plus it sends the BeneMut potions the way of the "Potion of Gain Strength" and such.

Please offer only substantial and constructive criticism, particularly in GDD. Thanks.

For serious, then, there are clearly two proposals in one here.

1. Increase the number of interesting choices (and consolidate inventory to boot) by combining potions with disparate effects into single potion types.
2. Radically change the mutation game, in this case by preventing players who want to keep a set of positive mutations from using a useful item.

Personally, I love (1) but hate (2); in any case, it seems straightforwardly more productive to discuss these topics separately.

I would prefer merging cancellation and cure mutation, as they cover the same flavor aspects (cancellation reduces magical contamination as one of the effects), while still aiming for the same goal of the OP to make cure mutation useful to drink in combat situations and offering tradeoffs (drink now to cancel bad effects/reset contamination or save for later to cure mutations). I would prefer a mutation system revamp over either, but that's not on topic.

BeneMut replaced Gain Stat because it's more interesting.

Malmutate is a bad mechanic and should be revamped, as was promised would happen when rMut was removed.