My first impression is that this is so incredibly complex and autistic that bitcoin has zero hope of ever becoming mainstream.
Here is an actual balanced overview of the drivechain softfork proposal:
https://cryptoadventure.com/drivechain-the-bitcoin-upgrade-to-end-all-altcoins/
Best reason against it is that if a truly private sidechain is created it will lose its special status with the SEC
Discussion
We will learn. you will just need to use it one day not ;)
Hopefully you're not excited for this, because I sure am not while also wanting Drivechains.
lol. ngl, kind of a good point