Agree that the Messi thing is a silly example and not useful in the discussion. I agree that UEFA would be highly wary of banning most top European teams from the CL, because it's a very slippery slope, especially given the dissatisfaction in some quarters (Spain and Germany, basically) with the current format of national league and European tournament. But I would think that if a team like City or PSG (or Monaco) blatantly broke FFP regs, they'd be exactly the sort of clubs that UEFA would be willing to ban. They'd be sending a strong message about the efficacy of FFP, whilst also avoiding taking any of the traditional participants out of the competition or pissing off the influential heavyweights like Bayern or Barca.