This was one of the things posted in the most recent newsletter:
2. Can we have a vendor that does not charge by the hour?
Yes we can come up with an additional vendor that doesn't charge by the hour but instead takes up house storage and charges a commission percentage only when the item is sold. This type of vendor will be in addition to the original style of vendor.
I just want to say, THANK YOU! Please make this a reasonable commission that isn't just focused on taxing the super rich. This could help bring back some regularly stocked player vendors.
Also, consider each item not taking up one full storage slot. I imagine a good number of people will switch to this new vendor. It'd be rough for a player who runs a vendor mall to maintain their one house when it's filled up by players selling items.