IF's genocide run used to intrigue me (once I even sent you a post with my ideas!). But I'm glad you're not focusing on no mercy, because at the end of the day, that's not where the heart of IF, or Undertale in general, is, or should be. I'm crazy excited about the "Endgame" arc, even though I have literally no idea what's going to happen, and it's not just me. Guess what I'm saying is, you have your priorities straight, Dorked. Good on you :)
Yeah, that’s the thing. Fundamentally, there’s... not a lot of interesting ground to cover in an Inverted Fate genocide run. Sure, it’d show the characters from different angles, and there are other themes I could explore, but there’s just no way to make it work without it seeming forced and contrived.
There are plenty of AUs that are ONLY genocide-based. I think the Undertale fandom can survive an AU that only focuses on neutral and pacifist. IF’s upcoming plans are already going to take us into 2022, by my current estimate (because of production time, plus possibly video/playable parts for a few specific moments). By the time IF is completed, it’ll be a story significantly longer than base UT, covering a lot of different themes and ideas,to the point where I think it can work standalone w/o the need for a murder spree.
If anything were to fill that niche, it’d be the Waterfall Incident.