Would it be viable to let people purchase gear from dungeons? Perhaps via the Calamity Salvager or a similar dedicated NPC whose stock is determined by your dungeon-clearing achievements. (We already have the "Mapping the Realm" achievements in place to support such an approach.)

It seems like a potentially ongoing way to have players spend a fair amount of gil, mainly for glamour purposes. I'd certainly go for it.

Make them expensive so it's not really viable to cash them in for GC seals, but for people with gil in hand and a need for a specific piece, they can choose to pay for it instead of running dungeons multiple times to acquire it – which would also cut down on how many other income-generating items (sellable items, gear, tomes) are created out of thin air by the act of running a dungeon.

I think a problem of the game is that every activity tends to generate currency almost as a side effect of what you're actually after, but there's very little reason to channel it back into the game. At most you're buying things off other players (crafted from materials they gathered for free, made with tome-purchased items or won from a gil-generating treasure hunt) and only a portion of funds gets taken out of circulation that way.