One of Traveller's true strengths, which is shared with BRP/Cthulhu/Pendragon/Cyberpunk and other skill focussed systems that don't use character levels, is that there is little problem with asymmetrical parties. When character level is an important thing and affects a character's ability to keep up with the group, it becomes important to keep parity between characters. I didn't encounter the concept until a few years after I started playing RPGs and have never much taken to it. Traveller character creation is, of course, among the most asymmetrical ones in the RPG world. You can end up with a 22 year old with basic training and background skills and not much else going for them except their health, or a grizzled old veteran with far too many terms and failling hand-eye co-ordination, but who's the best damn engineer in the subsector. And it does not matter.