With the upcoming realm switch timer, I don't really see how people can reliably trade gold from one realm to the other. I know it happens, but it relies on people not to scam (which is against the rules). However, should someone scam, it requires an investigation by GMs, which can take a long time to do. It would be far better if there was a way to trade gold between realms.
Something like you put in gold into an escrow account, the other player puts gold into an escrow account, and somehow you click agree on a trade. The amount is then locked and when you switch realms, the gold is then deposited into your account vault in the other realm. Thus, it isn't dependent upon knowing the player's name on the other realm (especially if you haven't created a character on that realm yet).
Something like you put in gold into an escrow account, the other player puts gold into an escrow account, and somehow you click agree on a trade. The amount is then locked and when you switch realms, the gold is then deposited into your account vault in the other realm. Thus, it isn't dependent upon knowing the player's name on the other realm (especially if you haven't created a character on that realm yet).