Let people be able to use the containers they've branded (or put a lock) on someone else's claims. That way people would bypass the hassle of setting personal claims at markets + ease the trades in general.
Scenario 1: A person ports to the Sevillian charter. He wants to leave his containers somewhere outside of the theft zone, but also to be able to pick them up/use them/take what is inside of them.
A trader dragged 2 large chests of linen clothes to sell. He'll have to leave his chests at the theft zone, which is not convenient since people might steal it. If he'll place it on the market's claim, he can say bye-bye to the chest for several hours until the market crew will get online.
Scenario 2: A noob barterstand owner could just drop his chests anywhere on the storage zone of the Sevillian market without the need to wait for a palisade to be built (2 days)/setting the claim (8 hours) and etc. which is quite challenging for noobs and the people who'd like to start trading straightaway.