Many of your requirements are met by Ditto (on Windows) and ClipMenu (on the Mac). The basic model is: Ctrl-V pastes like usual, Ctrl-Shift-V pops up a menu of every previous paste. Previous items can be selected and pasted using either the keyboard or the mouse. This gives you persistence, visual display of the clipboard, and keyboard and mouse interaction with the history. And it turns out to be insanely useful. Oh man. I would never go back.