We don't believe in the future of nations. A nation is an obsolete concept from times without global communications. Therefor pension systems should not be organized on a nation level.
The basic for a modern global pension system is the individual pension need and organization. The global pension system should be built-up in a subsidiair manner.
Layer one should be the individual pension. Layer two should be a regional solidarity circle. Layer three should be a global solidarity circle.
An individual pensionable should have a pension contract with a regional solidarity circle. The pensionable should be obliged to pay a percentage of his/her pension payments to the circle and the global layer. And with that should obtain certain rights from the regional and global community.