I really think that the Enneagram should get rid of the notion of wings and integration/disintegration. Here is what I propose:
Ideally, an Enneagram test should not have you choose one type over another, but rather have you check off all the statements that apply to you (for every type). This way, you can see all types that are relevant.
In theory, the type for which you get the highest score would be your integral type. This is your main type.
All types for which you score above a certain percentage (e.g, 50% (but are not your main type) are your auxiliary types. The patterns of these types can be found in your behaviour, but none serve as your core motivation.
Finally, the types that are not really evident in your behaviour are your shadow types.
Here is why I think this is a better model:
1) People can behave in different ways in different situations, so often, there is often more than one core type evident in one's personality.
2) Test results indicate that many people get higher scores for types other than their wing. Therefore, it doesn't make sense to refer to someone as a 5w4 when, for example, there are far more Type Nine aspects to their personality than Type Four, as the Nine traits would have more influence on their personality and are nowhere to be found in the categorization of their type.
3) There is no evidence to believe that, for example, Fives integrate to Type Eight when healthy. In fact, if the Eight is naturally opposed to a Five's basic personality, then the individual would probably never integrate to Eight. However, there is no reason to believe that such an individual could not still be healthy.
In conclusion, I think that the Enneagram is a good model. I can clearly see the Enneagram types of a lot of people, and I can't say that for a lot of other systems. Also, almost every kind of motivation I can think of could theoretically fit within the motivations of one of the nine types. That means that it's a complete system. Finally, the Enneagram uses levels of health for each type, and this adds another dimension to a person's personality that should be adopted by other systems. However, the wing and integration/disintegration theories are not logical, and so I think that they should be replaced with what I propose.