I don't understand what is there that I can't do with rectangles in Emacs 24.3 (or even way before).
I can already kill (C-x r k), yank (C-x r y), replace (C-x r t) text in rectangles, insert text after the rectangle (C-x r z) or at the beginning of all the rectangle lines (C-x r a) or their ends (C-x r e).
What else is there?