Let's not turn this thread into the other one as we are not talking about the same thing.
Balance is a good thing when it makes it easier for the DM to challenge the players without killing them.
Having said this, in true sandbox play, I do not want my megadungeon design to be completely constrained by treasure parcels and XP. Many of the solutions proposed on the other thread show how deep this problem goes.
I don't want a megadungeon where the encounters and treasure magically change depending upon PC level. I want a place where I can site interesting encounters, that make sense, with some treasure,
ahead of time, and then see how they play out when the PCs try to confront them. I want to truly reward clever play, not by making the monsters harder, but by allowing the PCs to roll monsters over essily if they are capable of doing that. I will also site monsters that are very very difficult challenges for the PCs and see how they take those on.
In short, I want a game where player choice is King, not balance. All I am saying is, if in the course of designing my dungeon, there is a conflict between increasing player choice (and vermisilitude) and between game balance, then I will choose the former every time.
In a more linear and plot focussed game this problem doesn't really rear its head because player choice is not such a priority. I have DMed such games and they are great fun, I just want to try this style of sandbox and it has needs that are totally incompatible with
4E's style of balance.