that's a lot easier said than done.
Not only would you have to get past the Swiss guard, you would also have to get past NATO.
so even if you convinced One Nation or a block of Nations to invade the Vatican, it would be impossible to get past the UN.
the only practical way that y'all can even remotely accomplish this a way neither I or the rest of this board can endorse would be a constant string of assassinations against the Popes.
You have to remember God gives us the leaders we deserve. Until the West gives up its delusions on liberalism and fascination with other isms you will be stuck with a line of liberal and leftist Popes.
of course the only correct answer is to become orthodox and starve the hierarchy of the funds it needs. Eventually, when everyone begomes than the Vatican will begome with it and return to Chirst's Church