Make them ALL QL 1 so anyone can use it. They would work like the ones in back to the future (2 i think). They can't go over water, but it would be a fun recreational thing to do in the game. You can have races through Rome park with other players and stuff. Perhaps even enable contests with the skate boards!
Something like tony hawk Skater games. it would require massive amounts of coding, but would be well worth it.
Games in games rock.