Here are links to the 3 levels that will be offered:
https://mini-lp-live.s3.amazonaws.co...ct+2019+PT.pdf
https://mini-lp-live.s3.amazonaws.co...read+V2+Pt.pdf
These levels are fixed. All you can change are colours and wheels. So, if you want Level 2 plus HK or sunroof, you have to go for Level 3. Also, if you want any shade of blue, apart from Enigmatic Black (which is more black than blue), you're out of luck.
Seemingly, the reasoning is they don't want people speccing weird cars and then cancelling them in March, leaving Mini with some potentially difficult to sell vehicles.