Isn't doctype still required by the spec in HTML5 in order to be "proper"? Perhaps I'm mistaken but I thought I remembered that it's technically 'required'.
It is, but I'd argue that people wouldn't even notice that the document is in quirks mode.
I think you'd really only want a TITLE tag so that it appears as a tab name. Anything else is really optional for people and you'd only really need BR, A, and IMG