If anything, you don't even need a second service account, you can simply have an alt on a different server and a friend who is ready to pay few minutes for a trade between your main and alt character. That's it.
Also, the reason why we can't sell things on other servers is much likely the fact that retainers' names have to be unique inside a server so placing something for a sell on another one can seriously mess up things, rather than the wish to prevent some kind of economic harassment because uhm... it's not like bots exist just on one server. If cross-server selling was available, nothing would've changed really just as almost nothing really changed in economics when they released cross-world visits in general: there are still servers whose prices are higher, and there are still people who aren't interested in jumping from server to server in order to buy cheapest version so they just buy it on their home world for whatever price listed.