> It would have been expensive, but all characters should have been fixed size 64bit values.

It would have been a non-starter, and then we'd all be dealing with Shift-JIS, BIG5, and FSM knows how many different codepages to this day. UTF-8 is about as elegant as it gets, though Java and JS still managed to fuck that up too (they both encode every codepoint outside the BMP as surrogate pairs in UTF-8)