Perhaps a little too "non-granular".
But OTOH, a basic "familiarization"-type skill that automatically comes with background in career makes for a good idea.
(E.g. You start with "Career"-0 {or perhaps "Career"-0 and "Subfield"-1} in your 1st Term, and get an automatic increase of 1 level per term in-service. It covers general knowledge, things you pick-up, odds and ends, trivia, details, etc.)
So a Scout or Merchant or Spacer might be able to make a desperate appeal to that as "
Operate (Spaceship)" in a pinch (having been in the service for so-and-so long) as a type of "limited" form of Jack-o-Trades as a mitigant against either the untrained penalty (on a skill-level vs. penalty mod basis) or as a default 0-level in the task, at the referee's discretion, depending on what the specific situation is.
This could also work with other careers like "Marine-3" for 2-3 term Marines, "Army-4", "Agent-2", etc. in their particular areas of expertise and background.