I fly for a living but I also have my own single cessna for weekend flying and i DONT have an instructors rating. My cessna is on the N reg where I've been told there are no left/right seat requirements for private ops providing the aircraft has dual controls (my mate who owns a flying school asked the FAA specifically). So now I put people who want to look out the window in the RH seat but if they express an interest in flying I let them sit in the LH seat.
I can see how it would be an issue for a pilot with 50 or 80 hours to swap, but to be honest, I found it took me a couple of trips to get used to the RH seat and I don't even think about it anymore.
My advice is, if the CAA allow it and the pilot is happy he has done a few circuits in the r/h seat then there's no problem. I wouldn't get all anal about not being able to see instruments properly. your supposed to be looking out the window. don't look for complications where they don't exist!!