To be fair I think there is quite a difference between someone who owns a 'share' (be it an actual share, a beneficial interest, or a use interest) and just some punter who has chartered an aircraft. The later certainly has no understanding of this difference between a public and a private flight and rightly should expect that the service is provided to public transport standards, whereas the former (like most of us) should understand the difference.
I believe you can't do a fractional ownership programme (i.e. Netjets) under a typical JAR country's regulations and that NetJets registers the Euro aircraft in Portugal because the Portuguese have specific regs copied from the FAR that enable this.