Why can't they do what The Elder Scrolls Online did at first launch?! They had TEMPORARY severs set up to handle overflow, literally called "overflow servers" until the population stabilized. And they have only two servers, a European megaserver and a NA megaserver. I was usually thrown into the overflow server during peak times, when a spot would open, you'd be zoned into the actual server. Everything functioned, all the NPCs were there, you could gather and craft, and work on quests and whatnot while on the overflow server.

--Lucifer Mink