The NPCs felt the need to make it extremely clear that their currency would not be redeemable at other grand companies. That however, is in fact, a perfectly good solution to the problem.
They could solve the Ul'dah problem by launching the grand companies grand opening simultaneously with Ishgard. That being said, it's also possible chocobos and airships may solve the distribution problem altogether.
You might, but that's not everyone. I'm not saying the rewards need to be exact parallels, but why is it you are so against each class being represented to some degree in each company? Maybe conjurers can find staves and wands at the Twin Adders, robes at the Immortal Flames and accessories at the Maelstrom, for instance.
The NPCs did make that clear, but I assumed that was just for now, since you can join all three companies.
In the future I could see a potential problem if they make the missions ACTUALLY challenging to where you would need a group, but all the Conjurers are in one company for the conjurer rewards and you just have all Ul'Dahians without mages for their grouping needs.
I'm not entirely against it, I just feel there needs to be a reason to join one group or another, aside from convenience.
Really, if they just add a universal market ward, this would all be solved because the only real reason people flock to Uldah is.. well where else you gonna go to buy and sell? It's this games Jeuno.