The game doesn't seem to track who "owns" an item. It seems to track what player is allowed access to where the item is stored. If that storage space (house, Company Chest, etc.) is shared between players, then anyone with access can withdraw the item.

I also doubt it could be set to allocate portions of a shared storage to specific players. The closest you'd be able to get is something like the Company Chest with tabs, where access to a tab can be assigned to a rank as opposed to a specific player.

The only thing I see on your list as being a possibility is increasing the tenant count.