I think we already did this before - back in 2015-ish. transfer character-accounts from forum-accounts should cost: Plat-Gold-Sub cards. Benefit for both side - the server (as you use more sub-cards) and new players.
It's currently against the rules to sell accounts for IG GP. However, the 'loophole' you could use is to train an account for someone else for a fee (IG cash/items only). However, this is unmoderated and would be at the risk of both parties.