Dg800,
You have a very different interpretation of the rules than that put forward by the more Northern and Western based people. It would be useful to understand a bit of your background and reasons for your assertion. For instance you may be a Milan based aviation lawyer familiar with the detail of historic national and EASA law and judgements, on the other hand you may be a newspaper reporter trolling for a story.
I have no idea what laws might exsist in Italy on the subject, and given some recent criminal convictions or ATC, Pilots, and Geologists - I can imagine the law is quite different to the rest of Europe.
Certainly in the US and UK (the two areas I am quite familiar with) it is routine for officially sanctioned flights to let the passenger have a go (now many of these will be with a civilian instructor, but some are with just a CPL or military pilot or in certain cases a PPL).
Most 'official' events have some aspect of commerciality (like a trial flight or an Air Experience flight) and hence of some regulation that will typically require a CPL.
In the UK and the US, the legal logic is very clear.
1 - An aircraft has a certain specified required crew complement
2 - All required crew members must be appropriately licenced rated and current
3 - There is an individual who is the pilot in command who is responsible for the legal compliance and safety of the flight. In the normal course of events this role can be transferred amongst the qualified individuals by mutual agreement (and sometimes by legal precedent - such as the case of an ATPL allowing a PPL owner to land at the wrong (restricted in the actual case) airport)
4 - everyone on board who is not required crew (other than the legal transfer referenced above) is a passenger regardless of the ratings/licences held
None of the above says if passengers are or are not allowed to operate any aspect of the aircraft. Even in Italy I would expect the passenger to be allowed to operate the overhead lights, doors, air vents etc. Within the Anglo Saxon tradition, something must be explicitly prohibited for it to not be allowed. My understanding of some other legal traditions is closer to only specifically defined acts are legal all others are prohibited.
Thus we end with the position in the UK and US that the PIC is overall accountable for the safe flight, all required crew members must be licensed, but no restriction on who can operate which bit of the aircraft. So you are right, a Pilot could jump into the right seat of a single control aircraft and let a total novice fly the aircraft from the left seat. The novice would not be breaking the law (he is not acting as a required crew member without a licence, the required crew is in the aircraft and in command). Of course the pilot is guilty of reckless endangerment as he has chosen to place himself in a location where he is unable to exercise his PIC responsibilities to ensure the safe and legal (in terms of navigation, compliance with clearances etc) execution of the flight.