"And again, you can't offer a "genuine IR[35]-proof contract". IR35 is a smell test: if it looks like an employee and smells like an employee then, for tax purposes, it is an employee; no matter what bit of paper it signed."
That's the problem, what constitutes the person being an employee?
HMRC dont have a firm set of rules that you can use to determine your status - yet.
Literally all this will do is put rates up and change the way that contractors work to be less like employees. If HMRC firm up the definition enough to say "If you do x, y and z you are an employee" the next day you will have contractors refusing to do x, y and z without a price hike.
Also as others have pointed out.. If they class me as an employee Ill be looking for pension contributions, and will be invoking the working time directive when told I need to work more to get projects in early.
Biting the hand that feeds IT
