I agree, we need a beautiful normal world, and then we could start the others. But I just wanted to start thinking about it.
There is two issues with your idea:
First its really really early for that discussion
We have so much core engine stuff to work on. You can speculate or even better make cool suggestions but please do not ask. Simply because we don't know yet
Second this suggestion is pretty much a fix for MC. But when we are that far into the future we maybe don't want to be any longer so similar to MC.
With that said why not think outside the box here for a moment shall we?
First we also want Dungeon Keeper influences. Anyone of you played that game or are you all too young? If you never played it GET IT NOW. Secondly Dwarf Fortress.
So and if we are talking about Heaven and Hell why not do elemental dimensions (Fire, Earth, Wind, Water) Or more esoteric stuff (Life, Death)? Biblical themes might be interesting as well, 7 sins anyone? (Lust, Gluttony, Greed, Sloth, Wrath, Envy, Pride) Ok I admit getting there trough a dark portal is very much Full Metal Alchemist like
Anyways what I wanted to say is there are so many things we could do, just don't always think about Minecraft
And we need some more time. However i really really would love you guys to extend on your ideas. Make a real story out of it. Make it interesting!