Something I think is more of a convince more than anything else would having the joint bank either be larger or adding a different section it all together
( The Main Reasoning )
1. So you can have food, Potions, and other essentials that should be used by both parties based on the limited amount/production of said items.
2. Reduces the amount of communication required ( aka, I don't have to ask if my partner has spare food or specific potions ), I can simply look in the chest and see we are out.
( Also In all honesty I did not check to see if this suggestion has already been made, Also I ask that if you have any other reasons why creating extra space/new system would be beneficial to state it - To increase the likelihood of it actually being added - If you have the opposite I would also love to hear it - )