I'll just quickly say my peace. Disclaimer: I have not read this entire thread.

I think the vendor stalls, while a very cool idea, don't work very well.

There is something very frustrating about endlessly searching for an item, or trying to compare prices, to make the best deal.

While an auction house system is very efficient and easy to navigate, it's also very impersonal and seller unfriendly.

Ac2 had an interesting way of doing it by having several "mini" auction type vendors that weren't all linked but resided in major cities. The vendors auctioned only specific item groups such as trade reagents, or gathered resources, or quest items, or weapons, or armors, etc... it was an interesting mix between two systems of vendor stalls and auction house.

I don't know the answer to the economy thing but I hope the vendor system changes as its current form is just hard to work with.