I don't believe that downtime WAS due to registration.
As you'll read elsewhere in the Forum or on our Twitter, PWO suffered a server outage earlier this month where the web server crashed and went offline for a few days, taking down the websites during that time. The in-game maps are hosted on the same server, to reduce load on the main game server (which remained online during the same period, hence why the game was still playable). This was nothing to do with opening registration and the timing was an unfortunate coincidence which resulted in the registration period being extended.
Should we be required to take the game offline for the purposes of registration - something the new system should allow us to avoid doing - it'll be the game server that'll be taken down and players will not be able to login at all during that time.