Two major things jump out at me in this story;
1. "repeated concerns have been raised about the fact HMRC will be classifying people in employment law as employees, but not giving them any of the associated benefits" - This seems bizare. Who would want to do a contract where you can be removed with zero notice, pay 20% corporation tax, 40-50% income tax, no paid holidays, no sick leave, no safety net? It sounds very much like an "at will" state in the US, maybe that's the point?
2. "The measure is expected to bring in £3.1bn in additional revenues for the Exchequer between 2020 and 2024" - does this take in to account the drop in corporation tax which will happen when contractors leave the UK, or switch to perm roles? From what I've read there's about 1.5m contractors in the UK, so that works out as £516/year/contractor, which seems a little off to me ...