Yes you can change nation. But regarding Outpost warps... hmm I think you have to do them all over again. Since you havent delivered any supplies to say Sandoria oupost in qufim yet. Only for Winurst. ( shoot me if im wrong).
But this one of the "downsides" of playing as windy nation on Nasomi. Fewer ppl playing as Windy = less OP owned by windy.
I know you keep the rank when switching. (on retail you did). And have met ppl on Nasomi that have rank 10 bastok , but is now rank 4 Windy for example.
But someone who has done the change please comment, so the thread starter knows what to do
Thanks !