Yeah, I'm not sure if "worldbuilding" is quite the right word to use because I might be interested e.g. in what a sci-fi cast of characters would look like in 20th century Europe, or baseball team AU, or, like, a western or noir genre movie, and I'm not really interested in the worldbuilding aspects (especially for mundane/real life settings) but just how the cast would slot into a fairly established world and character archetypes. So it's a bit of an unusual use of "worldbuilding" in that case where the world is already pretty established and worldbuilding isn't a focus. But yeah, I get what you mean!

Anyway, thanks! I will do what I did with AUEx and just nominate a range of characters who could be interesting but say I'm not particularly picky what characters/ships are focused on.