The issue of shops called for a separate post.
1st concern: People want to sell items to chests that are full.
Look at it this way. You're trying to sell ice to an eskimo. If a chest is full it means that item isn't selling (has no current value to traders), therefore the shop isn't going to pay money for something that at the time is worthless. I often give a courtesy announcement of item amounts that have been bought (and can be restocked by you for trading power). I intentionally avoid stocking items myself to encourage others to get their own trading power by stocking those items themselves. Try farming items that people are looking to trade for because there will be space in the shop to get trading power if people are buying them. Only when items run out or are not being restocked by traders do I step in to make sure the supply remains good. Encouraging people to use the Trading HUB for selling AND buying will only make the HUB more functional and beneficial for all.
2nd concern: Everybody and their mother wants a shop.
I'll be stupidly blunt, maybe to my own detriment, but it's purely honest. There isn't a need for multiple functioning shops. Note the functioning part. If you want decorative shops and the like, go for it, but one properly-managed trading HUB is all that is truly needed. The reason is this: people will determine what price they set their time at, each item will have its cost based on that price and the time it takes to get the item, and a good shop will buy the item for that price. The sale price should be at, or just above, the cost to get the item. One shop that has this figured out, and adjusts a bit as value fluctuates, is enough, especially given teleporters. More shops makes things convoluted as people don't want to search for where people bought from so they can sell. I think some people just want others to visit their towns, so just think of a way other than jacking with a stable economy.
I enjoy maintaining a great Trading HUB. It takes more effort than people realize, which is why the initial flood of fresh shops ends with them being unstocked or outdated with time. The truth of the matter is this, I'm not the best builder, the best recruiter, or the best forager; I often put off my own builds for lengthy periods of time, or indefinitely, just to make sure that better builders than I have the materials they need to bring their creations into reality. I love providing the best Trading HUB I can, I love improving it based on feedback, and I can't imagine what else I'd do on the server if was unable to continue doing it.