Hotseating sounds niche but helpful for some. It would give another use to singleplayer. Right now you can just do it manually by telling the other player to "look away" but that's hardly effective. 

Maybe a LAN gamemode would work too as an alternative to hotseating. LAN isn't *too* hard to set up, and doesn't necessarily require access to the internet. If you have "the tech kid" in the family (that's usually the one who plays a bunch of games) then they can set it up in a way where the players can't see each other's screen!

The issue comes in needing more than 1 PC device... but yomi hustle seems very easy to run so it doesn't matter how bad it is, just as long as it can run it.