The regulatory burden would simply be too much and given the increased opportunities for abuse, I can only imagine. I am speaking from experience and have already seen this with Meta Groups - rampant abuse, infighting and chaos all around. It's already difficult enough to enforce Cultural Protocols and the real life variables ban, frankly, I think this would be a nightmare, with some people likely to use proxies and other methods. I think the potential chaos would not just burden Moderation but players as well. There's often a lot of resistance and repeat offending in cases involving multiing, Cultural Protocols and real life variables.
As for allowing multiing just in order to allow certain players to 'protect' their creations; every player has to weigh whether that desire outweighs their interest to explore other opportunities. What about the reverse - the fact that so called 'blandocrats' would be equally enabled to greater blandocrising opportunities through multiing? Certainly the culture of the country will always be protected by Moderation, I assure you a lot of time is spent on this.
As for Nationmasters, Nationmasters don't have access to the game engine and would not be able to tell where players are multiing and I think, driven by political considerations (if you will), would be unlikely to 'snitch' on multiing players in their countries - they are elected after all.