I agree that a check flight, where a prospective hirer is being checked out by a (presumably experienced) PPL has a bit of a dubious status. Indeed, on the one hand you designate the prospective hirer as PIC, on the other hand he's being checked by someone who doesn't have had formal training to train or check somebody, but who does limit what the PIC can do (particularly he limits the ability of the PIC to refuse to take the check pilot as passenger).
That is what I am trying to get across. You can not say that a pilot needs to be checked out and then let them be pilot in command
before they have completed the checkout you require.
This is single pilot ops.
The only way that two crew members can log the flight time on a checkout is for one of them to be an instructor.
As llanfairpg said previously, if two pilots are flying together and one has the ability (by agreement) to override the other pilot by taking control then the person with the ability to override the other is the pilot in command. Passengers do not have any authority to override a pilot in flight. In fact it is clearly defined as being illegal.
Saying that if you see something dangerous or that you do not like will cause you to take control is saying very clearly that you are taking responsibility for the safety of the flight and that you will through whatever actions are necessary ensure the safety fo the flight. In other words you are saying that you are the pilot in command. There is no other way to look at such a statement.
Having decided who is pilot in command then the other person is either dual or a passenger.
If the pilot who needs a checkout is pilot in command then the rule requiring a checkout has been broken because they are pilot in command without complying with the requirement to be checked out.
There is no system for and it is not possible to change the pilot in command during normal flight time.
Regards,
DFC