I'm not sure if this would be feasible to implement, but I think making the chat logs within hired merchants remain in the store and be available for viewing (kind of like the personal shops where the store owner can see the chat) would be helpful for people wanting to leave offers on items. This way someone selling an item can go offline and come back and see offers their items, and others can see what the current offers are.
I love this idea, I've been wanting this for a while. It's a lot more convinient than trying to catch them online or smegaing to see if they're on an alt.
That would be great to be abale to wake up in the morning and see if there's anyone intrested in my stuff but for a lower price or trade for something else...