EricB in your example you note Fi and Ti serving suppressive roles. This makes a great deal of sense to me and seems to align with what I have noted in myself. From your understandings, would this also mean that Fe and Te are mutually supressive? Ne/Se and Ni/Si as well?
As an aside-wrt children-I watch my 3.5 year old intj a lot. It is interesting as he sort of cycles through his functions-the top four Ni, Te, Fi, and Se, but he isnt really using them in concert. He will Ni switch really crazy things and pop out with Te explanations that are utterly incorrect. Other times he will be tyrannically Te. "No mommy, this is this and that is that!" and push me out of the way to take over a task and be hyper senstive to shifts in schedules or be obsessed with catagorizing things (with that crazy ass ni underpinning).
He will then be very, very sweet and clingy-even say really sweet things. (few people get this sweetness from him <3 ). However the funniest is before bedtime...he just gets more and more active...manically so-Se I presume. Not spastic-but active. jump jump jump jump run run run run jump jump jump jump yell yell yell yell, till I drag him to bed and off to sleep he goes. normally he is actually pretty reserved and quiet, so the pre bedtime activity is very odd.