I think it's positive to have them opt-in to a common payment system on top of any national system they might currently have. Redundancy (and the possibility to leave, though potentially crippling) is politically attractive to many.

Ideally they drift toward consensus by skimming the best protocols, but it also permits incremental development where e.g. a smaller system might nominate itself as a test-bed for a specific feature, or bounties for external firms to compete over simultaneously.