I really don't see a problem here... Four lots of thirteen, at 10,000G a piece... That's still a fairly hefty sum to be bringing in...
Dusk Leather isn't even a rare item; It shares the same rarity as Platinum Ore and other random crafting materials. The rare items are the furnishing/minion parts. Dusk Leather is currently the most lucrative because of a better demand, since it has multiple uses (three pieces of gear?) and more people are likely to care about it since furnishings are only going to appeal to a small portion of home owners. Iron Giant Cores are going to be the long term money maker on Airships, see: Blue Bird/Tiny Nutkin/etc.
Oh I'm not ignoring the issue, I've simply be clarifying your mistake. You seem to think that the i180 accessories being missing is somehow a shocking new direction the developers are taking, when it simply isn't. Crafted accessories were at the "cutting edge" of raids in this game at launch. That was it. Patch 2.2 added Second Coil, crafted i90 gear with no accessories, the i90 accessories came in 2.3. Patch 2.4 added Final Coil, crafted i110 gear with no accessories, the i110 accessories came in 2.5.
The only difference between i90/i110 accessories, and i180 accessories, is that the i180 ones might suffer from limited supply and might suffer from poor meld options. Call me optimistic, but when one of the major pieces of content in 3.1 has "access to new gathering nodes" as a reward, I'm willing to see where things go, rather than resorting to doomsaying. I sold enough i90/i110 accessories, long after Second/Final Coil were cleared, not to be particularly worried...
This is perhaps another issue I have with what you're saying... You seem to be under the impression that the only demand for materia is the 1% of people who bother with endgame raiding... I mean, we've seen the numbers of people who've attempted A1S and those weren't that impressive. I'd love to know how I'm currently selling IV's and III's, when crafted i180 is apparently completely worthless. The simple fact is that there is a greater demand for materia than just the top 1%, this applies to gathering and crafting too; I've seen plenty of people maximize their melds on such classes and then proceed to do nothing with them. Presumably these people care little for the fate of i180 crafted gear, but they're still going to be fueling demand for gathering/crafting materia.
Seriously, right now I'm getting crappy III's pretty much every day, and they're selling every day. Who do you think is buying these? I can't really fathom who is buying my Battle Dance III's, but I'm not going to complain at the extra 10~20k being brought in when the Tiny Bronco parts being used long since payed for themselves.
You may want to give up on that, then. Airships are locked behind Housing. Housing has serious supply issues. SE simply cannot lock anything substantial behind them with that in mind, it would upset far too many players... Airships are simply the next tier of Gardening, another thing which is old as dirt yet still somehow makes money. That's how I view them anyway. Gil is the point of these things, be glad they at least added Grade 3 Actions to boost Airships somewhat. Honestly though, given my bank now has more Gil than I'll ever know what to do with, I'm seriously considering giving my members a weekly paycheck or something, which is potentially a nice draw (maybe they'll actually decorate their damn rooms).
Going back to my original post though, I think the best bet for them "balancing" this, if it's even viewed as required, would be an Allowance system just like Treasure Maps; You can board the Ishgard Airship once every 18 hours, but you can use a Free Company Airship whenever, provided it isn't on one of the current Voyages. Either Free Companies get unlimited rides there, or having a Company Airship just grants something like an extra Allowance; I can get twice a day, instead of once.
As awesome as "Final Fantasy XIV: Skies of Arcadia" would be, I cannot see them doing this with the current housing shortage. Although it would be nice to have some kind of open world siege based PvP, in which anyone can take part, but Free Companies can bring Airships (and later Primals, because that was promised back in 1.23.......) to the table... Though the popularity of PvP in this game leaves me somewhat doubtful we'll ever see something that awesome...
Wouldn't have to be Airships though, come to think of it, could just be siege weapons made in the Workshop. Effectively make them consumables, and made from items the Airship brings back, and they'd have a constant demand for things like Cassia Logs. Though again, I don't think PvP is popular enough for that...