Nah, it's a certain Imp. Fucking calling it. I mean, how anti-climactic would that be?
"The real reason I never left that first dungeon? The economy and socio-political aspects of my island nation are solved, bud. I can't even play my role as the big bad because at least half of the adventurers are horny perverts who just want some fat cat ass or tail pussy while the other half get so far into debt that they end up a breeding toy in that bar. At the very least, I can screw around in the first dungeon and maybe sometimes get some dick."
Biggest issue is she'd have to be an almost unstoppable force of sexual prowess. Kotone has the hypnosis down. Oni twins are basically multi-partner/interchangeable fetish content. Amy is the "Jesus Christ, how horrifying" fetish stuff covered. Vili is tits town. Mika is borderline ass perfection. We have at least 2 types of plant girls who fulfill that role. Elves for vanilla shit. Nara got them hips that definitely told a few lies.
Honestly, it'd either have to be an existing character who satisfies expectations, or it has to be something in the ever-narrowing pool of "safe" fetishes that hasn't been done yet. I just don't want another Monster Girl Quest where the endgame waifu is boring af while the stuff leading up to her is some Cthulhu-inspired bs.