Hi Malc
These are very good points and I can tell you love your Agattu and rightly so.
I would say to hold the persons driving license or ID would be a good idea, but at ones own discretion. Usually the person trying the bike arrives in a car, on their own bicycle or with their partner. This should be deposit enough

Please make sure that the person testing the bike does know how to ride a bike before letting them try it. You are responsible for your own bike.
Having seen 1000's of bikes demonstrated at shows and on our premises I have only ever witnessed one incident which was due to a very powerful hub motor folding bike, this had a tendancy to wheely if you pulled the throttle without sitting on the bike. Thankfully nobody was injured and nothing was damaged. The Panasonic system is very user friendly.
However, before letting someone try the bike it is always a good idea to provide basic safety advice and information such as where the brakes are, on/off switch and point out local obstacles such as busy roads or potholes.
Best regards
Scott