I think a centralized ls bank could work for mass crafting mats with a feature that allows ls crafters to request mats with a predetermined price point. then those who have the mats but do not need them could deposit directly to that person's retainer. Very similar to the existing retainer system when one is looking for mats but at a heavily discounted ls price.
Example: ls member needs ice crystals for his leathercraft, submits a request for 500 crystals to the ls bank at a predetermined price of 50 per crystal. I, as an alchemist, check the ls bank request and deposit 500 crystals, and receive 25000 gil (minus any bank charges) for my trouble. The crafter is happy to spend minimum gil to rank up his craft and I am happy to help a fellow crafter, even when we cannot be on at the same time due to time differences.
