Many people want the whip swinging back. I agree with that, since that'd require bigger skill than doublejump or superjump, and replacing those with it could perhaps introduce the much needed actual difficulty. But no rings please, that was just dumb, especially to have those hang in air. Make it swinging from parts of the environment like rooftops with wooden beams, chandeliers, chains etc.
Another thing would be difficulty select from the start, like I think bloodlines had, as well as the hard difficulty to be actually harder (new enemies like I think cv1 or 3 had in second quest), not just cheap (idiotic level caps or one hit killing moves).
Then, for all the extra modes to be as important as the main mode, like bloodlines or rondo were, with own story, ending, even items.