MartinCh,
I may be looking at this too simply but if you are doing an "introductory flight" it is either a trial lesson or it isnt.
if it is a trial lesson you need an FI rating, if it isnt a trial lesson then its a commercial flight and you would need to fly for AOC holder and have OPC + line check etc.
as far as I know thats it or am i missing something?
CF