I think this is a good idea. It allows owner of rare items to monetize rare items that they are not using atm. It has no risk of 'friends' running away with the item. It allow casuals to rent it for a limited time to complete so difficult missions.

the only point I want to add is that once item is rented out, it cannot be rented to another player until the lease has expired

Neat idea, but ultimately depends on how SE sees it