The character can have a job as a politician, but he has to rely on the skills he got in the military to do it.
Using this as a starting point, I went looking at the actual skills available for a Diplomat or Bureaucrat.
The following skills are not found in LBB1 and have been ignored from the careers:
Carousing [Bureaucrat, Diplomat]
Instruction [Bureaucrat, Diplomat]
Interrogation [Bureaucrat, Diplomat]
Liaison [Bureaucrat, Diplomat]
Recruiting [Bureaucrat, Diplomat]
The following skills are found in LBB1 the Bureaucrat, and the Diplomat:
Admin [Bureaucrat, Diplomat]
Blade [Bureaucrat, Diplomat]
Computer [Bureaucrat, Diplomat]
Gun [Bureaucrat, Diplomat]
J-o-T [Bureaucrat, Diplomat]
Vehicle [Bureaucrat, Diplomat]
The following skills are found in LBB1 and the Bureaucrat, but not the Diplomat:
Brawling [Bureaucrat]
Leader [Bureaucrat]
The following skills are found in LBB1 and the Diplomat, but not the Bureaucrat:
Forging [Diplomat]
Streetwise [Diplomat]
Gambling [Diplomat]
Vacc Suit [Diplomat]
So based on this, I suggest that if your character has two or more skills from the following list, then he/she may be cut out to become a politician after retiring from the service:
Admin [Bureaucrat, Diplomat]
Blade [Bureaucrat, Diplomat]
Computer [Bureaucrat, Diplomat]
Gun [Bureaucrat, Diplomat]
J-o-T [Bureaucrat, Diplomat]
Vehicle [Bureaucrat, Diplomat]
... If you also have either Brawling or Leader, then you are more of a Bureaucrat-politician.
... If you also have Forging, Streetwise, Gambling or Vacc Suit, then you are more of a Diplomat-politician.
As a side point, it also reveals out how little difference there is in the skill sets between a Diplomat and a Bureaucrat ... they are more alike than different.