I've thought of having a family-run merchant ship culture, similar to what's in Citizen of the Galaxy, in MTU, but haven't really worked out what types of ships they would use. There's a lot to think about, especially when taking into consideration their culture, laws, family ties, economics, minimum ships for new families, families that join or split, old families split between a handful of ships..., connections, enemies... It's almost like writing up the history and culture for an alien race. I kind of see them as Merchant Space Gypsy's who follow the credits and are very serious about safety and family.