I wish there was a way to break/destroy the recall stone, there are so many scenes that could be turned into permanent, mind-break bad ends.
I agree. And this seems entirely within the game's realm of possibility when you consider that Venefica (if I remember correctly) is able to negate the effects of the recall stone using her magical prowess. Naturally, as the game slowly progresses, future characters will be much more powerful than those you would fight in the forest and dungeon so it seems like it should be easier for other characters to disable recall stones as clearly, methods exist as proven by Venefica.
But, I think I recall Threshold stating that they prefer everything to be more consensual in nature and so, a bad-end would likely be more of the opposite. He clearly tries his hardest to try and write it as though none of those female characters are aware that the recall stone has its flaws, that perhaps they are disinterested in the MC except for a quick lay. He makes many of the girls more submissive so that it seems an unrealistic decision that they would do such a thing as disabling the stone's ability, or just has them all share this weird code of ethics which prevents them from wanting to enslave the MC, where this is the first monster girl game I've ever played where it is considered wrong and immoral for a monster girl to have a plaything. There is the tengu girl who talks about taking the MC home as her slave but then there is the recall stone as a device which conveniently prevents that outcome, making her victory dialogue pointless. There doesn't even need to be an expansive enslavement system but a bad-end scene after losing X amount of times to certain NPCs does not seem unrealistic.
-Shizu, even though she is more submissive, could keep the MC as a permanent 'training dummy' for her students.
-Vivian could keep the MC as a brothel employee, or if he loses to Nara, Vivian could give him to Nara as a prize for successfully impeding his progress when attempting to travel upward the mountain, etc.
I'd just like to meet some actual female characters who are enslaving male travelers, where that fate could also be MC's if he were to continually lose or meet prerequisites, instead of just having the girls resorting to the brothels or shoehorning it as a romance scenario such as with Kaia the manticore, and her addictive venom.