Tafoid filed a bugzilla entry for the copy/paste problem with some systems (I think it depends on the delay some machines expect between sequential inputs)
concerning the original post, I think that he talks about something different. However:
1. copying and pasting RAM content requires some sort of snapshot format to be created, and however I think you can already use the debugger for that
2. BASIC tokens manipulation can be added to imgtool (I think coco supports this already if you need an example)
3. copying the screen content is something that I have no idea how could be implemented across the various different systems: one should probably intercept all the accesses to the RAM/VRAM and select the specific ones (it also reminds me too much the old hack used for c64 floppies, so that thinking to it already gives me nightmares...