Propose house rule:
If a PC has completed a career and taken the dedication bonus, he will always have the option of playing a session 'in' that career, even if he is developing a new career.
i.e. An ex-soldier, who is now a Burgher, finds his town under attack from Orks. He manages to get into his old chainmail and frees his sword and shield from their mount above the fireplace. He then marches out to help defend the town.
He can now socket those Tactic talents that have been idle for years.