Any materials/Tips for running one shots?

I got a party of players who are enjoying the campaign I made, and everyone is having a good time, but...

They are glancing over at the other liscences they DIDN'T take and are sort of pining to try out other mechs briefly but don't wanna compromise their campaign builds.

Any advice or material for running quick one shots for them to test out and play around other mechs/builds?