I doubt that would seriously fix the problem at hand, the fact there's nothing to really spend gil on (that's actually taken out of the system) would mean those who have millions would eventually build gil back up in no time. I myself have only been playing about three or four months and I'm sitting on a few million gil I don't know what to do with.
I'd say making vendors sell more attractive wares such as cobalt materials, weapons, armors and dyes would take more gil out of the game in the long run. But to be honest vendors would need a new type of system to compete with the prices on Wards, the base prices would need to be reasonable to low, but it would require an aggressive enough price scale that we can avoid market flooding, price campers, and making the wards irrelevant.
However, to avoid price fixing based off vendor prices or sell rates (which became an huge issue in FFXI) vendor goods should not incur a maximum limit to the price it can rise. If any of you are familiar with playing FFXI back in 2005 or so, rental chocobos had a similiar uncapped pricing system. There were time's prices reached well over 30k+ gil for chocobos and that's kind of what I'm aiming for in this type of system.
Proposed Scale Per Purchase:
Rare/Unique Items: Constant (Does not change in price)
Unstackable Items: Armors, Weapons, etc. Incur a 5%~10% (debatable) increase per purchase off the base price.
Stackable Items (12): 2% Increase per purchase.
Stackable Items (99): 1% Increase per purchase.
Stackable Items (999): Constant (Does not change in price)
Dark Matter (All Grades): Constant (Does not change in price)
Reduction Rate: All non-Constant items fall 5% per Real-Life day at JP Midnight until the items low base price is reached.
Resell Rate: Selling an item to a vendor will be sold for the base resell price, however it will lower the % of the item respectively for the next person purchasing that item.
Example 1:
Cobalt Ore sells for 200 gil at a vendor.
Person 1: Buys a single ore for 200 gil.
Single ore is bought so price increases by 1%.
Person 2: Buys a single ore but price is now 202 gil.
Single ore is bought so price increases by another 1%.
Person 3: Buys a single ore but price is now 204 gil.
There are some exceptions based on buying in bulk giving people a slight discount from buying from the vendor, but the effects are instantly calculated and applied towards the next purchase.
Example 2:
Cobalt Ore sells for 200 gil at a vendor.
Person 1: Buys a stack of the ore off the vendor 19800 (each ore is purchased for 200 gil instead of the 1% increase per individual ore).
99 Ores were purchased so next purchase price is increased by 99%.
Person 1: Buys a second stack of ore immediately after the first purchase paying the vendor 39402 gil (nearly double).
99 Ores were purchased so next price is increase by another 99%.
Person 1: Buys a third stack of ore immediately after the second purchase paying the vendor 59004 gil (nearly triple).
As a minor suggestion that might prevent any other issues from occuring, having the price of items sold by vendors change and update on a server wide scale instead of an individual vendor scale would likely cope and prevent any sudden market flooding that might occur from multiple individual sellers.
Example 3:
Cobalt Ore sells for 200 gil at vendors in Uldah/Limsa/Gridania
Person 1: Purchases a single ore for 200 gil in Uldah.
Price increases by 1% in all cities and vendors selling Cobalt Ores.
Person 2: Purchases a single ore for 202 gil in Limsa.
Price increases by another 1% in all cities and vendors selling Cobalt Ores.
Person 3: Purchases a single ore for 204 gil in Gridania.
I know its far from a perfect system, but if SE seriously intends on balancing the economy and getting the excess gil off the server, they have to have vendors with attractive wares and a good supply and demand structure that's on a comparable level with the market wards, but not so much it dictates ward prices or makes the market wards irrelevant for vendor sold items.