Given the issues with gold sellers and their resulting bots, the only viable solution is to cut the link between the gold seller and gold buyer. Remove any ability to transfer gold between accounts and soulbind items received via the mail or guild to prevent their resell.
This in no way affects players ability to transfer between their own characters, interacting with the auction house, or even buying gems.
Only certain individuals would continue to use bots as only their account could gain from it. Without the sellers, Anet could better focus on removing these remaining cheaters.
Introduce a server type with the changes for new players or transfers (subject to gold limitation to discourage advance buying). If successful, existing servers could be transitioned in some fashion.