I think #4 (no liability for independent invention) would effectively eliminate software patents by itself. I like what's there even if it seems unlikely to ever be implemented.
Which allows interesting strategies. If you put a smart person in the right scenario with the right hints, he will reinvent whatever you want. You just have to keep him in the dark until the flash of brilliance, and you have a patented-idea farm. It might make a good movie.
He's not going to invent a new cancer drug or a cooling mechanism for jet turbine blades, unless you fund him with a few hundred million dollars while he's at it. Or even something like MP3 that uses psycho-acoustic models built on empirical testing.
Sort of. Not "whatever you want", but certainly a huge chunk of what has passed as patentable inventions in software. But some inventions truly are novel and difficult, even in software, though they are incredibly rare.
I think #4 (no liability for independent invention) would effectively eliminate software patents by itself. I like what's there even if it seems unlikely to ever be implemented.