I like the ideas proposed. More materials need to be sold at the guild. Making certain items only purchasable once a higher rank has been obtained would hurt scalpers who know they can turn a profit by buying out a guild and just bazaar/AHing it and I don't care for scalpers.

Another way of removing the market for scalpers is to create NPCs that do the same thing basically.

Make scalper NPCs outside the guild who have infinate supply & sell the same items the guild sells. Only difference is they sell it for the MAX price the guild can sell it at (only goods the guild restocks are sold there).

I think there are several items stocked by other NPCs already, sold at a slightly higher price. If the npc is tied to a region to get restocked or conquest tally rank, leave his prices alone. If the npc sells the goods all the time with no restriction, raise his price to almost if not as high as the scalper.