Upon further thought about some kind of Unified Theory, I have realized a major flaw in the logic of the primary idea. To create some kind of non-varied theory, that would, in essence, require 1) an agreement among professionals and 2) a change from theory to process/fact. The latter point is distressing because we would be changing a theoretical construct (something that can be further developed or altered) and change it into a globally-accepted idea. If something is accepted by everyone to such a degree, it becomes de facto fact.
People are not the same! Sure, some theories have shown empirically better results than other, but those results are most likely pulling mostly within two standard deviations of the mean. There are always outliers. To use such a Unified Theory would leave these individuals out in the cold and would staunch further development by professionals. Sure, there would be fringe development, but such action would be seen as para-science by professionals and would include only minor numbers, decreasing its academic potency.
This is not to say that a therapist-based theory is not worthwhile to cultivate (keeping in mind that it would not function for all clients). Instead, I think that it is of great import for any therapist to understand their own core methodology with room to alter for fringe cases.