`xclip-mode` looks like it should definitely be included by default. `cua-mode` is tougher because it messes with the default keybindings, making you type C-x twice (or Shift-C-x) for the large number of keybindings that start with C-x. That might be better for newcomers though, and bring more people to Emacs. Personally I would disable `cua-mode` if it were default.