If I made a Tube line, where would it go?

 At the moment, there are 11 Tube lines, as well as TfL Rail, Overground, Trams, Cable car and DLR. London hasn't had a new Tube line (unless you count the Elizabeth line as Tube, even though it has a different roundel) in over 40 years. This is the line I would make if I was given the opportunity:

First off, I would replace the High Wycombe to Marylebone Chiltern service with this Tube line. This would create better links to central London from High Wycombe, Wembley and Marylebone for relatively cheap. It would also stop at Brondesbury or Brondesbury Park Overground station.

Next, I would bring the line up to Mornington Crescent station. This would relieve stress on Camden Town station as there would be another direct way to King's Cross St Pancras, where the line would go next. This would then join up to the Piccadilly line and share the stretch of track up to Green Park, however wouldn't stop at Covent Garden. 

After Green Park, it would go along to Sloane Square station, renamed King's Road. It would then go to a new station, King's Road West, around 51.48458483715844, -0.17548151633188858. After that, it would go to Imperial Wharf before terminating at Wimbledon Park.