This thread made me think. I have never thought that one could undergo a real crucifixion "to suffer for yourself and get sexual satisfaction". Crucifixion meant being tortured to death and this, in my opinion, would never result in any kind of pleasure for the victims, from the sexual point of view. It was much more terrible that we can even imagine. So people undergoing crucifixion would be just unwilling victims.
If I think about my motivations... well, it is difficult to explain, but this is so fascinating to me, and it has been for years. If (IF) it would be possible for me to undergo a full Roman style crucifixion (with nails, flogging, everything) and at the end magically -magically- get out of it without physical damage, I would do it. Of course this is not possible in reality (at least up to now), and this refrains me to do so, but if in some strange phantasy world, it would be possible, I would offer myself immediately.
I know that it would be terrible and gruesome for me, but I would do to experience it in itself (feel how it would really feel), and, above all, to give pleasure to the executioners and to the onlookers. The best pleasure in their lives. Probably this would be the driving motivation. It is not easy to explain, and probably, much more difficult to understand I know, but I guess this is something like the deepest analysis I am able of...