In Re: Mercenaries.
a good stable long term merc unit will match army, flyer, or marine pretty darned well. Bad ones will be pirates...
Careers list:
I think MT had a pretty darned good one.
Military: Army, Navy, Marine, Flyer, Sailor, Scout
Paramilitary: Pirate, Law Enforcer, Barbarian (which really sems to be TL4- Army), Merchant
Civil: Hunter, Rogue, Belter, Scientist, Diplomat, Noble, Doctor, Bureaucrat.
Of these, it can be argued that Hunter, Rogue, Pirate and Belter are merely lifestyles... but I think the 18 MT core are a really good sample.
Now, my houserules add 3 more: Farmer, Civil Aviation, and Colonist.
21 careers... but given that 3 per page fit nicely under MT...
I think MT CharGen is about perfect on choice levels and skill levels.