I would make subtypes based on the development of other functions - in the case of INTP's, Ni, Se, Fi, Te, and maybe Si and Fe. I have a difficult time accepting the idea of the shadow function etc because so many people don't tend to adhere to that paradigm.
I know for me I would say my order is more like Ti, Ne, Si, Ni etc. There are probably a lot of INTP's that have much higher developed Fe and/or Fi, allowing them better emotional intelligence. In my case, I often feel like I have a more developed sensing function (probably introverted sensing) then some of the people here - while I enjoy theory, brainstorming, and abstract thoughts/discussions, I tend to have a very strong sensing-like skepticism that, after all the theorizing and 'Ne' tangents are said and done, brings me back down to earth to really question how valid something is (i'm a stickler for supporting evidence, as some people may have picked up on). And, of course, I have plenty of theories as to why this may have come about.
I guess if I made some further subdivisions, it would be something like (and using INTP as example, even though subdivisions of this type would be applicable to all types):
1. Ti, Ne, sensors (Si or Se) - the more practical INTPs. These are the skeptics, the one's that formulate intricate and complex theories of their own, but ultimately do not endorse them if they don't have any real world support.
Si - quiet creatures of habit. These types might have the hardest time coming out of their shell, generally finding a comfortable niche and staying there - which may add to their seeming procrastination. This type might have strange, almost OCD like rituals done merely for the sentimental value, because having something that feels regular is comforting. These types might have their minds invigorated by doing menial tasks - things that don't require a lot of mental effort, like taking a walk. A lof of the stimuli for their imagination is derived from things they have sensed in the past. May also be good at compartmentalizing, having several modes of operating 'saved' in their memory that can be brought about by recognizing the salient features of an environment.
Se - the experimentalist. These are the 'mad scientist' type of INTP, the one's that will stick a fork into the toaster, knowing full well what will happen, just because they wanted to experience it. They may be the slightly more outgoing INTP, enjoying the experience of life, even other people. While many INTP's seem content to read about an experience in a book, the Se INTP's would rather go out and do it - but still require time to themselves to sort through it. Their theorizing is perhaps derived from the world around them, wanting to see, smell, hear, touch, and taste new things because the external stimuli is what gets their imagination running - which means they may have a much higher appreciation of aesthetics and/or art and nature. They may be very adaptable, able to go with the flow and get the hang of new stimuli - unlike the Si type which may become overly sensitive if too much is going on.
2. Ti, Ne, feelers (Fe or Fi) - the emotionally intelligent INTP's. These are the people more in touch with their emotions, and are more likely able to express this, possibly in an artistic way - poetry, drawing/painting, song writing etc.
Fi - These INTP's have an appreciation of their own emotional side, allowing the Fi to 'warm' their cold logic in some ways. They hold their principles in high regard - even for an INTP - because their principles aren't always just because they sound the most logical (although they do, as a rule!), but because they have an intrinsic value to the INTP in question. This is also an INTP type which may experience some internal conflict, spending a lot of their mental effort trying to create harmony between their emotional side and their logic side. Just like to anyone with Fi, authenticity is important to them. Their imaginations are highly focused on ways they would improve the world - or at least some facets of it. These are the INTP types that might sometimes be mistyped as INFP's.
Fe - similar to the Se type, these INTP's may be more apt to be doers instead of readers. These may be the INTP's with a much higher aesthetic appreciation, enjoying novel external stimuli - including other humans. This may sometimes be the type of INTP with a larger circle of friends and correspondents. Being strong Fe, but still INTP to the core, they spend a lot of time thinking about the interactions of humans and their personal relationships (as opposed to cold mathematics or physics), coming up with theories about the motivations of other people. Fe INTP's are could often be the ones that are the most interested in personality type theory (along with other social sciences) because they are interested in how other people think and function.
3. Ti, Ne, thinkers (Te) - these might seem like the OCD type of INTP's to some. Like all INTP's, they create complex inner models of the world, but unlike most other INTP's, they also tend to project those internal models onto the external world. These would be the INTP's most likely to enjoy systems, perhaps becoming computer scientists, engineers, arcitects, or even doctors/surgeons. They may get enjoyment from solving complex puzzles, or playing chess or other games heavy on strategy. These are the INTP's that have very strong logic and reasoning skills, focusing on things in a very rational, often times cold and calculating way. Immature Te INTP's might be very stubborn or even closed minded and stand-offish. These are the type of INTP that may often be mistyped as INTJ, having much in common with them (perhaps this type is even where the distinction blurs into INTJ, rather then having a definite distinction between the two).
4. Ti, Ne, intuitives (Ni) - the archetype of the absent minded professor. Theory and abstract thought defines their lives. An immature Ni INTP might have a tendency towards fantastical thinking with no basis in reality, or even paranoia, their theories and internal worlds becoming more real to them then the real world. More highly developed ones are able to make sense of the world (and the cosmos) with ease. Abstract thought comes easy to them, and the pieces of a complex system seem to just fall into place for them with little effort. Insights may just come out of nowhere, their theorizing needing little to no stimuli to shoot off on multiple tangents. Because they live so much of their lives in their head - even for an INTP - they may come off as being very aloof and/or absent minded. Contrary to this look of aloofness, they are probably one of the most open minded types of INTP's, enjoying new ideas just for the exploration. I would say Einstein was probably an Ni INTP.
Anyone can feel free to add to these, criticize them, or change them around however they wish, I just threw them together right now, so I don't really have any personal attachment to them.
The problem is, even dividing a type further, based on the development of other functions, seems as if it could be divided even further. I'm sure people have also had a lot of influence based on upbringing (perhaps even birth order), the books they've read and TV shows they grew up on, the friends they have/had, the cultural, religious, and political atmosphere they grew up in so on and so on.
), and is able develop and mature as time goes on (and possibly even regress, due to traumatic experiences etc).
