This thread is frustrating.
You guys have a lot of good theoretical ideas. They sound very fun and it looks like you guys care a lot about them. Honestly, though, "good" concepts can turn out to be awful in practice, no matter how the good the execution is. There's always factors we don't see or know about until they come and bite us in the arse. It happens to me a lot with a lot of the stuff I prototype and design, and I reckon it's why a lot of people don't stay in the games industry for long.
I've stopped trying to thinking about ideas that are "X + Y" or "X but with Z" or just short ideas in general. If I can't write a detailed 5 page concept document on it that makes any reader know exactly what the game is like and fires their imagination to the point they're actively seeing exactly what I see while they read, it's probably a good idea that could never be executed properly.
inb4 "McJobless just wants to stuff on everything"; spending 10+ years of having ideas backfire in horrible awful ways and watching people forget themselves over while chasing a fantasy makes you kind of cynical about "good ideas".