Not all of them do. Vurture City has no requirements.Gold star would be cool tbh
Just make sure we have a hard map series to beat
Another thought, maybe some of the challenges wouldn't have to be "special requirement", but just a map string.
E.g. Red Run: [No special requirements]
Shri Tra Savern
"Funkytown" <-- Notice the sarcasm
Notice: This does not need to be a challenge. This is just an example. I think doing this in a row is insane.