since you’v already distinguish players to trusted or untrusted status, you can use it to limit the bots
1.dont let players do goldexchange at goldshop when their accounts are unsafety or at untrusted status.most of the bots are useing weekly quest to get gold.
2.dont let players exchange 3 tier materials at shop,or change the materials to bound.
vpn ban really waste your time. there are more than 30 vpn companys in china, you should focus on the bots and the cheaters,dont waste your energy on the vpn companys or the normal players.