U+0020 is perhaps the weirdest character in Unicode. Most of the time it's used to separate words, which is arguably a kind of mark-up. But sometimes it's used for other kinds of formatting. Also, if you were to use explicit mark-up for words I have no idea how you'd handle punctuation. Perhaps writing should be redesigned from the ground up?

But meanwhile, though we'd all love to see the plan, let's stick with the mess we're used to.