I almost feel like this is a silly post...but yet I felt compelled to add my 2-cents.
Labels, or titles, are a nice and easy way of letting people know where you generally fall, but to force people to stick to those labels and never grow, or explore, is confining and boring. Have you always been exactly what you define yourself as now? Do you really see yourself not adapting or changing how you define yourself later in life? And why do you feel such a need to stick everyone in a neatly labeled box to define them. How dull that seems!
I think that trying to fit all the variables into nice tide Dom or sub category, with everything else being switch, is an oversimplification. In your example of straight,gay,bi for instance you state that if you kiss a member of the same gender you are bi...but I for one have kissed another female and would not consider myself bi at all. Sexually I am attracted to men, but in multiple situations I have kissed a girl. Once just to try it (and lips may be lips, but girls kiss way differently than boys do), and on other occasions because my partner "requested" that I do so.
Sexuality is more of a scale than a one or the other box. In fact in research most people are found to fall somewhere between "totally heterosexual" and "totally homosexual" and yet very few identify as bi-sexual because their preference is for one or the other.
I feel that roles within BDSM world are very much the same. Some may not identify as switch, but would be willing to try a role-reversal with their partner. Or, just be curious to understand the other side of things better. Again, speaking for myself, I am a submissive...but my partner suggested that iit would be good for me to understand the role of Dom, so I have taken a few small forays into being the Dominant with him. But, I realize that it doesn't "fit" for me. In this case experimenting has cemented my role, but since I have experimented would you still call me a switch?
Titles are handy, but I think letting them define you and make your decisions for you is to cut yourself off from experience, and unlike you I am a huge advocate for experimenting and exploring. After all isn't that why most of us are here in the first place?