Do you agree that the fairest system would be to combine everyone's utility functions and maximize them?

No, I do not. I do not think that humans have coherent utility functions. I don't think utilities of different people can be meaningfully combined, too.

I think these issues can be worked out.

Ah, yes, the famous business plan of the underpants gnomes...

If so, do you agree that voting systems are the best compromise when you can't just read people's utility functions?

No, I do not. They might be best given some definitions of "best" and given some conditionals, but they are not always best regardless of anything.

CEV is about somehow finding the best compromise of all humans' utility functions. About combining them all.

What makes you think it is possible?