I made some quick mockup locations for new Marketboard locations that should be be equal to all.

Gridania:
Placed just under the Inn next to the airship because there's alot of dead space down there while still being close to the Grand Company and Aetheryte

Lominsa Lominsa:
Placed on the walkway just near the Inn that is right above the Aetheryte instead of being dead next to the crystal so it's closer to the Inn and Grand Company. Placing it here will also increase foot traffic around the Inn instead of the crystal while also increasing incentive to go to gridania and uldah for MB instead.


Uldah:
inside the Gambling Hall which is both close to the Grand Company and Inn as well as the Aetheryte. this will also open up a new path to the GC and Inn as well.


I personally like these location ideas for the MBs over how they are now but that's just my opinion. that's just my two cents on this though.