More pluggable textareas. I'd like to be able to use more emacs controls on all systems and even Mac only supports the most basic ones. I can't do emacs text highlighting and so on.
My point isn't just about emacs but that there are powerful text editors like emacs with powerful keyboard shortcuts and I'd like to be able to have more of that in the browser while I'm editing emails and blog posts and whatnot.
Yes there's that one browser plugin that allows you to open an emacs window and it sends the result to the textarea but I don't consider that a good alternative at all.