I just got a lightbulb moment, when you share a vault with a spouse, you can rarely trust them to not dig into your money...
How about when you share a vault, the owner of the property can allocate a percentage of the vault to their spouse, say the max capacity is $300m, the owner can set the capacity for their spouse to 50%, giving them $150m space in the vault, and neither can access each other's money. Basically splitting a vault into 2 secure parts, but the owner decides the size of the parts.
Just an idea :)