I've been thinking about this combination lately. It really colors the way we use our functions and it's somewhat difficult to find INFJ 6w5's. Sooo here's my little analysis of the lot, please tell me if it make sense for you other INFJ 6w5s out there.
The easiest way to describe INFJ 6w5 is caution bordering on paranoia. This is likely due to the thinking styles of the 6w5 coloring our cognitive function use...which alone is somewhat conductive of fear. For those that aren't familiar with Enneagram, Type 6 is generally plagued by anxiety in their search for a feeling of certainty and support. They're deeply afraid of being unsupported and they're generally cautious people. Type 6 people with a 5 wing has a little dose of Type 5 as well. Type 5 is the innovator, thinker type. They gather information relentlessly in order to feel certain about the world, which gives them a feeling of security. If we combine the two we get a cautious, somewhat fearful person that has a strong craving for certainty and knowledge. For them more than almost anyone else, knowledge is power. This becomes even more apparent when we take a look at INFJ cognitive functions under the influence of 6w5.
Ni 6w5: Introverted Intuition plugged into the energy of 6w5 is the primary source of the INFJ 6w5's fear as well as security. Ni is a future oriented function and it loves attempting to visualize the future, or various possibilities. Combine that with a good dose of classic Type 6 fear, and we see that Ni is a fantastic way to develop paranoia for these people. It's easy for this flavor of INFJ to get pegged as a pessimist, because they can always see what could go wrong. INFJ 6w5s are extremely good at predicting problems before they happen, which causes them to be in an almost constant state of anxiety. The 5 wing especially shows itself when the INFJ 6w5 attempts to gather as much information as he can in the present moment to try and know for sure if his visions of a particular outcome are likely. Situations in which the INFJ 6w5 using Ni go into blind are usually the most stressful for this flavor of INFJ and unless evidence turns them away from it, they'll almost immediately look for problems. It causes fear for the INFJ 6w5, but it's actually helpful in that it helps them to brace for problems before they even happen, resulting in a lot of "Gee, that wasn't as bad as I thought." moments.
Ni for this group of INFJ isn't all bad though. INFJ 6w5s often use it as a means of finding safety through fantasy or pure idealism. In freetime they may engage in drawn out fantasies in which they are safe, self assured, and certain, which alleviates many of their anxieties. A spiritual practice that allows for the possibility of transcending stress are extremely helpful for this group.
Fe: Extraverted Feeling on the INFJ 6w5 is where you are able to see them at both their best and worst. Fe is a group values oriented function; it wants to connect with the group and it supports social harmony. This is ESPECIALLY so for the INFJ 6w5. INFJ 6w5s often look to others for support, for good or ill. Remember, feeling unsupported and uncertain are there greatest fears, so in social settings they are extremely fearful of criticism or rejection. They are extremely cautious in social engagements in order to avoid losing friends that they don't even have yet. INFJ 6w5s may find themselves forming surrogate families among friends to feed their need to belong and to make others feel like they belong. Of course making friends isn't immensely easy for the INFJ 6w5 because they are quite naturally distrustful of others. For them to actually reach out to another, they must feel absolutely, positively sure that they're safe. This usually takes a great deal of time as the INFJ 6w5 uses her 5 Wing influenced Fe to gather information about the person until the person becomes predictable and thus "safe". The inherent contradiction poses many problems for the INFJ 6w5 in social engagements: they both want to be a part of and reject social structures. They want friends but at a distance, they want to belong but not completely. This is due to Type 6, which want security in a group conflicting with Type 5, which wants to be an innovator. The more evolved INFJ 6w5s calm this conflict through creating a loyal group outside of what's considered "normal" socially. INFJ 6w5s are very likely to champion the underdog.
Ti: Introverted Thinking gets a lot of usage for the INFJ 6w5 as the two Enneagram types are thinking types. Like the other functions, Ti both a source of fear and safety. More so than many other INFJs, INFJ 6w5 analyze everything. First they run it through their Ni, which usually either a) Gives a negative outcome or b) Shows the possibility for safety. The INFJ 6w5 will then using their Ti to gather and analyze information in order to determine, with certainty, what will happen. INFJ 6w5s are information sponges and they're probably the most analytical of the NF types. No idea just stands for the INFJ 6w5, they question everything, even themselves, relentlessly, running it through their Ti checking for accuracy. Obviously this 6 influenced Ti may be a tremendous source of self doubt as the INFJ 6w5 will question and analyze themselves constantly. On the brightside they are extremely self aware and humble. What they may see as a lack of self confidence is a tremendous gift of skepticism that stops them from becoming naive.
Se: Extraverted Sensing for the INFJ 6w5 is borderline nonexistent consciously. 6w5 are mentally oriented so INFJ 6w5s are extremely likely to ignore both physical reality AND the present moment. Funnily enough, strong sensory impressions (loud sounds, harsh tastes, or too much feeling) may be source of fear and stress for the INFJ 6w5 because it forces their minds to actually live in awareness of the present moment. INFJ 6w5s are usually future oriented and when they're not looking at the future, they're analyzing the past for information, or perceiving the present through their intuition which IS NOT living in the present moment.
So these are just a collection of my thoughts, theories and personal experiences as someone who both is, and has creepily observed other INFJ 6w5s. If anyone (especially other INFJ 6w5s) want to tell me how right (or wrong) I am, please make yourself heard!