I would recommend sticking with a skill.
Just off the top of my head, if you check out the Spacemaster Tech Levels, you could use that as your base Tech skill (treat as a related skill for up to tech level below, and one level above), and then have the subskills for each specialty.
Then the base skill would be all about general operation of things from that tech level, and then specialties would be for more indepth (i.e. Tech (Lvl4 = now), and Tech:Programming would involve how to program computer, while Tech: Computers would allow for repairing them.).