One of the big problems with this is there is no global shortcut for copy and pasting. At most there are the primary, secondary and selection buffers which applications can copy into and paste from. But each application handles the copy/pasting functionality in their own way. Or rather they typically let the toolkit they are using deal with it.

Klipper, the kde clipboard manager comes close to something like what you want. You can CTRL+C multiple times and it stores a history of everything, then you can assign shortcuts to cycle through the entries and paste them out again. All it is really doing is reading the clipboard when it changes, saving that value than essentially copying from that saved list when you cycle though it. So it would be possible to write something similar that has specific numbered buffers - but you would still be saving/loading into the primary clipboard which applications can then paste from rather than creating a new set of shortcuts to paste from each buffer directly into an application.