Instead of the dreaded "Not Want!" at the revelation that Padme is dead Vader should try to kill Palpatine as he no longer has any use for him, only to have Palpatine use the Force to fiddle with his suit and disable him.

Yes, the guilt that Vader feels at that moment should turn into anger against his "master" in the minute. What I think that could be done is that during the transformation of Anakin into Vader the Emperor could twist the mind of Vader so he don't feel regrets or remorse anymore and all he can do is to obey. That would make his return to good in the OT even more powerful because we know he struggles against the mind manipulation of the Emperor. Just an idea.