NC Launcher... you choose location of the server(not yours), NCsoft only has Blade & Soul in Europe, so.
it was only implied that you wanted to use the same account for both versions at the same time(They would only need to add a Classic Authentication server, and an extra button for Classic... then somebody is gonna want to use same account on Chronos and Naia at the same time... that's never gonna happen either.) I can use Live/Classic at the same time on 1 computer(obviously on separate accounts)... nearly EVERYBODY runs more than 1 account except you I guess, because the rest of us have access to both versions all the time, just not both versions on 1 account at the same time.
Make separate WH/Trader accounts, to sell items/watch world chat... for each server(0 toons on all other servers), then you can choose where you want to play daily on your Main account, based on server Drama or Raids/events/clan activity.