Rank, mission progress, and CP are stored separately for each nation. You can only use the stuff from your current nation (whatever that may be), but if you switch to a previous nation, you're back where you were when you left. (If you switch to a nation you haven't been to before, then you're rank 1 with 0 CP, and you even get the new character cutscene.)
Outpost warps are just plain *lost* when you transfer. Even if you transfer back, you don't get them back. On the bright side, two months after transfer and you'll generally have 80-90% of them back (newbie regions notwithstanding - but honestly they're not really worth weeping over if you're like most people who have them, and only *use* them twice a year

).