You'd be somewhat surprised on that point. Especially if you just take it such that everything is just trying to build up an s-expression. While the homoiconicity of the language is incredibly cool for macros and whatnot, I don't think you strictly need it. Especially not at the top level. (That is, if you made a language that "compiled" down to s-expressions, what is missing?)
At the extreme end, take a look at Dylan.
Though, I was really referring to your other points. It seemed every one of your "questions" is directly addressed.
But everybody defining their own syntax would not make a language "the perfect language". Quite the opposite, because nobody would be able to understand each other's code anymore. It would be the ultimate fragmented language.
And because of that, I don't think a perfect language is even theoretically possible. Everybody has their own syntactical preferences, and allowing all of them means fragmentation.
