(sorry guys for making so many threads lately.....! man, I am just bursting out a backlog of content)
It may be a mental metaphor to say that every Ji type is the prince or princess of their own private castle. But some Ji types actually do have a castle. 0.o
FiSe Enya lives alone in a castle (called Manderley castle):
Another example alongside Enya, is FiSe Michael Jackson with his fantastical Neverland Ranch:
These physical spaces hold a deep personal significance, and also a somewhat secluded attitude. The tendency for the FiSe (in particular) to form a personal space was first noted by Ayoungspirit in this post. Of course, I think it's not always this extravagant (it could be as simple as a really decorated tumblr page, or the Ji's room - depending on what's available)
This also applies to Ji in general within all hierarchies, as it is a function that is individualistic, concerned with its own private alignment and its own aesthetic or logical/rational crystallization. We could say that Ji, in all types, stands as the prince or princess of the psyche. It is not the king or queen with the responsibility of managing the kingdom (Je) but it enjoys the same royal status and aims to passively guide the rest of the psyche toward a type of morality, correctness, accuracy or (we might say) nobility.
The Ji type will aim for refinement of the self, and this pursuit can often become all-important. Often the ego becomes personally involved, and the Ji type will find their identity resting strongly on their ability to "be" and embody the aesthetic they so imagine. They may dedicate their energies toward expressing that inner self perfectly and feel a continual dissatisfaction when reality does not match the ideal.
This aim toward nobility & perfection can also lead the Ji type into a common dilemma. Ji's will aim to own their own feelings, own their own ideas and will often stubbornly refuse help or pity. They will aim to do things from their own power and in their own manner, and may consider it a failure of the self if they cannot accomplish something in the way they believe it should be done. In this way, they may become impractical, fussy or deadset on principle. In the most severe cases, the Ji type would rather fail and self-destruct than to do something outside of the parameters of their axioms. They may say "There is no point in doing it any other way" or "Doing it that way would defeat the purpose".
Nitpicky: Ji is the part of us that tells us something is "not quite perfect yet", and when this sense is strongest, the Ji type can find themselves incapable of producing or finishing any works, for lack of ability to settle with what is invariably a hair short of the original vision. Ironically, the Ji type may have their own creative flow reduced the more they try to manifest. As Ji is not a creative process but, in many ways, a subtractive process, what is easiest to notice is the lack in things -- where work for refinement lies. If the Pe and Je processes are not allowed to enter the creative process, the Ji type can find themselves utterly incapable of manifesting.
Heh. Or more seriously -- by the development of Je and Pe mostly.
Pe: Will add a level of tolerance for ambiguity, improvisation and incompleteness. It'll add levity to the overly-serious perfectionism of Ji. For example, some Ji artists can really clamp their creative flow by nitpicking each detail. But when Pe is properly integrated, then at some point the focus moves to creating/generating, rather than just reducing and refining.
Je: Will help in the practical department. If an assignment has to be turned in, Je will be the voice that pushes for some result, rather than "no" result. Je will also accelerate the production process by thinking about the consequences of not accomplishing, and using that as motivation to produce.
Also relevant might be to work through any emotional inhibitions which may be clamping a person into Ji. For example if a Ji-lead is also someone with obsessive compulsive, or a low self-esteem that causes perfectionism, then they'll have a harder time loosening up.
I'm impressed by the amount of meticulous work he put into everything, writing 14 books in code must have taken a looong time! Kinda reminds me of Jung's Red Book. It seems this guy may have been attempting to reveal the truth of humanity/reality using ideas from occult wisdom and alchemy. This all seems like a collaboration between Ni and Ji to me - from the psychology I'd guess he's likely Ni-lead. I agree with your notion about his functions, his eyes do look Ni/Se, and he could have Fi as well.