Very similar idea to another to allow shop modules on ships so that you can run a mobile trading post.
Here's what I would like to see implemented.
If your 'market shop module' was place-able only on 'ships' the vendor's building would actually be a ship docked to the station.
A very real problem with the current shop module is that it can contain many storage boxes worth of inventory and if destroyed or accidentally removed all inventory is lost. I think it would be better if your 'market shop module' had to be linked to storage boxes and the storage boxes would hold actual inventory.
The market shop module would show the sell and buy prices you set for any block and would show how many of those blocks are in connected storage boxes. When a customer buys or sells items, the items are transferred to or from the storage boxes to or from the customer. If there is no free room in the linked storage the market shop module will refuse any further buy orders, same as running out of credits. Player should also have the ability to set a maximum inventory for each block.
The credits stored in this market shop should have a player set upper and lower limit amount, and any amount over or under that should automatically transfer to or from the player. Lower limit should be set as default at zero unless a player consciously decides to change it to something else. All buy prices should also bet set to zero at default, sell prices can be set at server trading guild shop sell prices at default.