I think the GMless rules are probably a really good starting point at least! I'm not personally into solo games, so I'm not super sure how well it would shake out long term? I think if I were personally going to run games in Blister City solo, I'd probably lean on a system with some more specific solo rules like Stars Without Number or Starforged, just because they were made with solo players more in mind, and they seem to have way stronger like oracle tables and whatnot. If you end up running it solo as is though, lemme know how it goes!