[ericthered]

1, 6, or 7:

7a: as four, but its not an exact alternate of the solar system
7b: Two planets rotating each other very closely. You can say "moon", or you can say "Binary Planets".
7c: Its like the Trappist-1 system (or the wild dreams of it), and it has three habitable planets in close arrangement around a red dwarf in resonance orbits.

Considering Tide-locked orbits, I think leaning into that could be fun. I don't think a 17-day rotation is going to be that bad, considering the temperature ranges we get in our northern latitudes where the sun doesn't rise for a month or more.

The particle radiation is a bigger deal, but that's something I'm happy hand-waving for here.