Didn't the moogles choose to leave the forest and be more proactive helping out in ARR? We're not forcing them and only a few moogles would actually take this job (only one in each city?). There will be other moogles doing other jobs elsewhere.

However I do agree the delivery moogles look like they bit off more than they can chew (bags are too big/heavy). While the struggling to stay afloat is cute, perhaps they should stay in the air longer and only fall down once in a while? (in the trailer they're falling constantly).

Or since they're stationary it makes more sense to me that they put the bag down and just get your letter whenever you talk to them. We could have one traveling Moogle that has to carry his bag all the time and is constantly dipping in mid-air, going from moogle to moogle making deliveries. Seeing this moogle occasionally walk around town, or even be in a couple of cutscenes would make him more memorable, like Stiltzkin!