Improving the economy and store mechanics
As I've implemented my store, and we're engaging with our "gold coins" currency, I've noticed a few things that might make it better.
Whether at the store or at the depot, I was thinking it'd be great for people to send requests in. They go to the depot or store, and request, for example, a "powered cart." Then when you log on, you see the request, and you either choose to accept, deny, or alter. Alter means you're going to set certain parameters where they pay for half up front, or they provide all building materials, etc. You can alter the price etc. Once that happens, it sends a notification to the requester, and they can accept, deny, or alter. TO avoid the loop of unending alters, there should only be one alter for the requester and two alters for the builder.
Secondly, a note section in the store. The ability to type a note that someone can say "hey, i stopped by, saw you didn't sell this, could you sell this?" as a way to help the storeowner when he's offline.