Giving GMs bot-banning powers would just pile extra work on the escalation resolution team. For no purpose.

The best ways to beat the bots are system-based: fix the loopholes that allow teleport/trespass hacks; track patterns of automation on reported accounts. The best way of all is to track the flow of gil. Given that they have the capacity for complete knowledge of where every gil in-game comes from and goes to (not as individual elemnts, no, that wouldn't be necessary; we're talking about bulk flows here), it should be possible to ban RMT accounts (the bots that grind the cash, the bot-fed sellers and the cheating muddyfunsters who buy the illicit money, all of them) faster than they can make money.