As good an idea as this is, I think we need to re-think it.
Recruiters hold too many cards for this tactic of warnings to work. Even if we do manage to ban people (I'm assuming pre-emptive bannings aren't possible, they actually have to be in the region at the time?), it takes all of 5 minutes to create a new recruiter nation.
I think we should be approaching it from the other angle. Instead of trying to make the recruiters shorten their ads to allow the RMB to work, I think we should make the RMB work to stop recruiting from working. Looking at the RMB now the ad there are covered by a 6 hour window, less than one message every half hour. If we all collectively posted on the RMB (be that conversation about current goings on, or pre-made standard messages about an aspect of TNP life) I'm pretty sure we could make it so its unusual to have more than 3 recruiting ads on the RMB at one time. And who knows we might attract the odd person as well.
Any thoughts?