Look, L2, you typed well otherwise, so I'd not known that English was not your first language. In that, I apologize.
However, in your idea, I find the flaw in this: singling out and attempting to gang-upon an entire class on account of a group's skewed perception of the purpose behind PvP is, for lack of a better term, overly discriminatory.
For that matter, we should hunt down every notorious, or even one-time, random PK-er on the server, because it's not fair that they abuse the idea of 'surprise-attack' when the true sport and challenge lies in an open, properly organized duel.
That being said, I do find the number of Assassin Crosses in proportion to that of other classes to be disappointing; the last time I'd been on a server where that happened, it wasn't long before old-timers began leaving for more balanced servers, and the population dwindled to the few overpowered SinX still sticking to what they built.
If anything, the only reasonable thing to do would be to setup a parameter which began to weaken a SinX character after X-number of PKs. Obviously, this would be a high number, but it would, if nothing else, either slow the growth of the SinX population, or lessen the need for them now, as not many people really want to go through the trouble of constantly remaking a SinX because they kill too much with it.
That's the only plausible idea I have ready, and again, while I apologize for misjudging your mistake, I must stress that I have a strong respect for the English language, or at least what's left of it - I can't help being a Grammar/Spelling Nazi sometimes.
<3
@Versace: I realize this now, and have apologized.