SPI Universe had a nice little grid for modifying skills based on your experience with different planetary environments. TSR Alternity provided me with an alternative way of doing TLs Aftermath provided a talent system that grants a modifier to certain actions based on the talent you use. I keep tinkering trying to incorporate rules from other systems stress/coolness under fire from YZE, pushing a roll.

Mostly though I just run CT77 with boon/bane from MgT and T4 armour as damage dice reduction.

I am an almost blind Luddite but will happily support every Traveller discussion.