These are the basic careers “most related” to intermediate careers by Trait (i.e. the fastest way to get there by CORE rules):
Chamberlain (can switch at one advance): Agent, bailiff, burgher, messenger
Charlatan(1): thief, gambler, agitator
Investigator(2 advances): Forger, gambler, agitator, envoy, smuggler, student, and thief.
Merchant (1): agent, biliff, burgher, messenger
Physician (2 advances): student
Seer: Mystic
Scholar (2 advances): student
Witch Hunter(1): zealot
Thane (3 advances): courtier dwarf
Duellist (2): courtier, fop, pistolier
Knight (1): Pistolier
Marksman (2): soldier, bounty hunter, waywatcher, wardancer
Outrider (3): soldier, boatman, bounty hunter, coachman, commoner, dockhand, hunter, roadwarden, rat catcher, mystic, servant, witch
Sargent(1): soldier
veteran(1): soldier
Ambassador (3): Courtier, Fop, Pistolier
Demagogue(1): Agitator, gambler, thief
Herald(1): Bailiff, Burgher, Messenger
I did not include the specialist careers such as trollslayer, app wizard, etc.)