Insurance...
Although I can't recall the wording of any specific policy, I think it's important to consider the issue of insurance in this scenario in addition to the legalities regarding licensing.
I would bet, perhaps someone can confirm, that an insurance policy granted to a flying club / aircraft owner who allows their aircraft to be flown by others will include a clause requiring the insured party satisfy themselves of the competency in operating the aircraft of the person to whom the aircraft is hired/loaned.
Almost certainly the insurance company will insist upon some form of "check" being carried out (or in legalese "appropriate means of testing or so satisfying") and will most likely require the insured party to have in place a minimum qualification/experience level for the person doing the testing, and probably to notify the insurance company as to who these people are.
I suspect that this has much more impact on check-out requirements than strictly licensing issues.
As an aside, how many flying club members actually ask to see and read the insurance documents under which they should be covered?