umm, this topic is turning into a discussion about drafts. Please start another topic if you want to see drafts as part of the Worlds main event.
Getting back on topic....
So, if someone comes with a truly unique, powerful, rogue deck, would it be a disadvantage for those players to allow all players to change their decks for day 2? Possibly. But that's what competition is all about. You play someone. If you lose, you either modify your strategy or try to play better next time, or both.
It's like this. You show up with your rogue deck. It's essentially your "trick play." Do I let you "trick" me all tournament long without being able to do anything to counter it? Maybe for one day, but not for two days!
IMO, I really feel it would increase the competitiveness if players were allowed to rest, regroup, and re-evaluate their game in between Day 1 and Day 2.