The Traveller system while interesting is pretty bland in my opinion. At least with Star Trek and Star Wars there is a lot of source material available. Even Battletech has a huge amount of fluff and background information. For Battletech, it would be a situation of ignoring the mechs themselves. A game of people on the ground. Making a living in various way. For Star Trek, avoid being active duty Star Fleet. Maybe being an intelligence officer would work but avoid being bridge crew. Star Wars, the ships are small so crew requirements are minimized. Plus it has a lot of fluff available and ships plans are available easily.