Fair enough, but once it becomes nescesary to use the IR, why can't the RHS person take over being PIC? For example, if a basic PPL is flying along with his mate, in VFR conditions, under VFR, but is about to enter an area of IMC where an IR would be required, then the RHS person becomes PIC.
I've used this many times in the US, flying with VFR mates. Its fine flying out in the desert VFR, but pop over the hills into the LA basin, and the weather is !!!!!e. So I, from the RHS, pick up an IFR clearance to wherever, and we continue under IFR. From this point on, my ticket is on the line, so I become PIC...nothing magical, no officially signed document printed out in triplicate and filed with the FAA or anything......
Cheers
EA