you could do that but then in about a week they will all be tunneling through hacked machines in the US, then guess what you lost an easy way to identify them
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You should probably clear that out completely every week or two, atleast those names that aren't just a jumble of random characters.
Most of those characters likely had their accounts stolen by RMT or others and have since reclaimed them. SE won't delete these characters. As RMT tend to only use the same hacked account for a short period of time before moving onto the next, the adverts won't be coming from the same person for long. Meaning that 3/4 of the people currently on your blacklist have likely either gained their characters back, stopped playing, or have their account locked down pending investigation and reimbursement for items that were stolen.
The only real solution to teleporting bots is to prevent teleportation completely. In most MMOs you cannot teleport hack so it obviously is not an impossible task. Also this purely client side location check doesn't appear to make the game any more fluid than it's competitors, in fact it is quite the opposite. Obviously you can never truly stop bots but at least they wouldn't be as effective.