I think there’s a lot of truth in your theories. In the case of transgenders, you have to add the ultimate thrill of completely rejecting your created nature and God’s design and declaring yourself to be God…the original sin, “ye shall be like gods,” and declare yourself to have the knowledge or definition of good and evil.
That said, I don't think transexuals actually are consciously thinking about or are even consciously aware of what taboos they are breaking or that they are rejecting God's design.
I think they are just obeying the old Satanic maxim of "if it feels good, do it."