Limsa Lominsa being the perfect hub for the market, since the market board is exactly next to the main city aetheryte.
Gridania, it take 2 steps teleportation into the main aetheryte then taking the Leatherworker's Aethernet that is next to the market board.
Ul'dah, in order to go to the market board the fastest way, one has to go through through 2 teleportation and a zone. By zoning into the main aetheryte then taking the Adventurers Guild's Aethernet then having to zone into Steps of Thal.
What I'm suggesting is to add an Aethernet in Ul'dah that is relatively close to the market board that will reduce the amount of time to reach the board and serves other purposes.
The best position that will meet these requirement is to place the Aethernet in Steps of Thal (12,10) that is close to the market board and cover the upper side of Steps of Thal that has no Aethernet close by and is also close to the Husting Strips that can help into reaching the upper side of Steps of Thal.