Wow, it's been well over a decade since I looked at 1st edition, but I seem to recall that 2nd edition had a larger set of skills by a good margin (40%). I don't recall the exact differences: more Science skills, perhaps?
Once RMU is done, I'd love to see SMU, Star Strike, and Armored Assault unified into a single sci-fi RPG. A lot of it could be re-written and made more realistic/believable given advances in science and engineering in the last 30 years.
P.S. Please give me a reason to use anything other than Laser Cannons or MLA Cannons on my constructs, and a reason to use anything other than CAT 24, 26, 29, or 30.