What is the personality type of Paul? Which MBTI personality type best fits? Personality type for Paul from Gremoryl& and what is the personality traits.
Paul personality type is ISFP, so you'll probably have a hard time finding a good Doctor Who companion for him.
I'm going to go out on a limb and say that you should choose a female Doctor Who companion for your ISTJ type. There's a reason why the Doctor is portrayed as a male character. That reason is that the Doctor has to act tough in order to make the audience believe that he's an action hero, but he can't act tough if he doesn't have a female companion to act tough with. I think you'll find that having a female companion will help your ISFJ (Doctor) type to shine through.
But if you're still not convinced, then maybe you should try something different. Try losing the companions altogether and go for another television show with an ISTJ character. You'll probably like all of your ISTJ characters much better.