I don't see how adding a revolving door ban would help... They join the channel, see that no warez is allowed, and leave. They probably will never come back again. Banning them will have no effect.
What you should do I think is to do a 5-10 minute ban on users who ask for warez even after a warning. Consider this a 2nd warning. After the 3rd, just ban them as long as you want... You have no need for people who ignore rules.
I believe banning users in warez channels to be a bad idea. They may be a warez user, but they may also want some intelligent discussion about Palms and by banning them even before they join, you deny them of that luxury.