Haha, interesting. Unfortunately I haven't read the series for a while now, so my ratings will be a bit off since I can't remember every little detail about everyone's behavior.
Marco - ENTP. Obviously an
Extravert, gains energy from being around others and getting a reaction from them. I picked
iNtuitive since he's often able to see the big picture and is good with strategies (and can philosophically justify them, usually in a utilitarian sort of way).
Thinking because Marco will, if necessary, subordinate his emotion to the more rational or pragmatic course of action, as he sees it (being able to contemplate killing his own mother, multiple times, is evidence of this, methinks). And
Perceiving cause he's chill, spontaneous, and just kind of goes with the flow until he has all the necessary information to make an informed choice about something.
Cassie - ISFP. Wasn't sure whether to pick ISFP or ISFJ, but the description of the ISFP that I linked seems to fit Cassie a little better.
Introverted--she doesn't need to be the center of attention, is quiet, and prefers to work by herself with her animals, or with people she's familiar with.
Sensing because she's good with her hands? And I don't really get a "philosophical" vibe from Cassie, sometimes she acts hypocritically without concern for the greater moral framework for her actions, which are driven very strongly by her pacifist
Feelings of compassion for what's right and wrong. And
Perceiving because she takes it easy and doesn't need to plan everything out.
Jake - ISTJ. Heck, the description just fits him really well. I think most of the dimensions are fairly obvious with Jake, except possibly for the S/N? But Jake is really more of the "practical military commander" than the "innovative scientist general" (whatever that means) sort of guy, so that's how I justify choosing
Sensing over iNtuition.
Mreh, I'm tired. Maybe I'll finish this later.