It's a good and thoughtful post.

Going through the iteration, there will come a point when the human world is going to lose its last anime, its last opera, its last copy of the Lord of the Rings, its last mathematics, its last online discussion board, its last football game - anything that might cause more-than-appropriate enjoyment. At that stage, would you be entirely sure that the loss was worthwhile, in exchange of a weakly defined "more equal" society?

I wonder if it makes sense to model a separate variable in the global utility function for "culture." In other words, I think the value I place on a hypothetical society runs something like., where x is each individual person's individual utility, and c is the overall cultural level.

A society where a million people each enjoy reading the Lord of the Rings but there are no other books would have high sigma[U(x)] and low U(c); a society where a hundred people each enjoy reading a unique book would have low total U(x) but high U(c).

That would help model the intuition that culture, even in the abstract, is worth trading off against individual happiness. I think I would prefer a Universe in which the Lord of the Rings were encoded into a durable piece of stone but otherwise had nothing else in it to a Universe in which there was a thriving colony of a few hundred cells of plankton but otherwise nothing else in it, even if there were nobody around to read the stone. Many economists would call that irrational -- but like the OP, I reject the premise that my individual utility function for the state of the world has to break down into other people's individual welfare.