Just my opinion of course but both your desired characters appear to me to be outstanding specialists in their fields. They'd be very mature, very much in demand, and not at all likely to be adventuring. I see them as high ranking officers, instructors, retired, or something. Something very much not about adventuring
All you really need for them as Adventurers is (LBB1 only, ignoring the enhanced gen):
Starship engineer:
Engineering-1 (Add 1 level if you want to be the rare talented one who hires out to adventure)
Jack-o-T-1 (to cover all the rest of the skills you listed)
...bam, 2 skill levels, even possible in 1 term, without commission or promotion. Anything else is gravy and colour. Like a level of a weapon skill making them dangerous and a level of vehicle skill for getting around dirtside.
Space marine:
Gun Combat-1 (you pick)
Cutlass-1 (free)
VaccSuit-1 (allows BD and ZeroG, with competence)
bam, 2 skill levels (not counting the freebie), and again possible in 1 term without commission or promotion. Easily employable as a Merc, in high demand in fact with the VaccSuit skill (that will be the tough one to snag). In LBB1 everyone has brawling at equal skill, because there is no actual brawling skill

And again, any extra skills are your character's "interesting" background.
What are my chances of getting these combinations? Fair to decent, especially if I go another term or two, and I don't end up a geriatric (in your words iirc) going for the full skill suite you want
But you know, as you already have a set idea of what you want, and no fear in changing the rules, just make it up. Then the chances of you getting exactly those characters, with idealized characteristics to boot, are exactly automatic. About the same odds in fact (in my experience) that you will play exactly the same character (possibly with a different skill set) every time. Not saying that's wrong, I just think you're cheating yourself and your group of a lot of fun in stretching your role playing talents
Be aware though, if the ref allows you such, and your character is not some super-star but just a run of the mill scrub like all the rest, then all the other PCs will be just as special-average, as will most NPCs you meet. In other words, in a universe full of Skill-3 multi-talented adventurers, you won't be special, and the challenges you face will be exactly the same (after adjusting for skill) as the ones my character examples above face. And you're going to be wanting Skill-5 now, and about 6 more skills to boot
