Actually it’s not a bad idea. Just being able to “post” items and setting the “price” to a number of runes. If the buyer accepts the deal from the AH it removes the runes from his inventory and adds the item.
Doesn’t need to be an alternate currency at all.
Actually you make add an extra tab to the shared storage and have it be a “shop” tab. Any items in there you set a rune value for and people could buy from it. Would be like setting up your own store.
It’s not something I would EVER see Blizz doing, but it’s not a bad idea, and it would work exactly like normal trading without the hassle. If slightly more limited. Would be great for people wanting to trade down runes, or clear out space.
Let’s real here though… Blizz can’t even get the lobby or chat working… do you really think they could code a working player shop?