Now, listen to me before you start to flame, and let me be as clear as possible. It's not really your choice. Kretol literally rose this server up from the ground, and placed control in those who he believed would be able to control the server and run it correctly when he's otherwise too detained to do anything about it.
Sure, you may like the server in how it was different, but the powers that be have decided that it's wiser to keep away from that. Why? Well, have you ever tried to create your own universe. Because, let me tell you, I have, and it is a hard thing to do, even when only between two people. Add in more people, say 50, and you suddenly have 48 more people's tastes to take into consideration.
So, say that Kretol and Grakor decide to, say, conquer Zul'aman. But, hey, some people don't like this for one reason or another. Suddenly, bam, drama everywhere. Then, guess what? Either, the people running it either ignore the drama and keep moving, which makes more drama, or decide to not do it, which creates players not liking eachother, which ultimately leads to more drama.
And if we allow one person to change the world? Well, at what point does it get ridiculous. People who lead something, or do some other important thing; Will they be able to stay on the server for as long as it runs? What happens when the person has to leave for personal matters. Does the town they were running turn into dust?
Or, what else do you want to do? Create a revolution against Stormwind? Maybe take over Karazhan? Destroy a town? Great, either you get killed in the process or you just lose interest in the full thing. Sure, being able to make your own world is great, but when does it become too much, and how do you know if RP will stay here? How do you know that it won't just become another useless place?
Then, there's another thing. Servers can only take so much spawned objects before it starts to lag. So, if every guild is allowed to create their own town, what if there are too many guilds? What happens to the guild bases? Do they just disappear? Do they get renovated? Maybe I don't get exactly what you mean by changing the world, but that's what I understood.
Now, onto Prestiges. Well, there's nothing stopping you from rolling whatever you want on retail. /shrug