I think the best would be an interface, where the patient isn't told if the doctor on the other end is human or AI. Tell them that they are going to do multiple remote exams with different care providers for the same illness in exchange for free treatment, and payment for the study.

If you're worried about not catching a legit emergency, as in something that can't wait a day or two for them to complete the different sessions, you could have a doctor monitor the interactions with the ability to raise a flag and step in to send them to the ER.

I'm pretty sure that wouldn't pass IRB.