It seems clear to me that both drivechains and liquid use a federation. The mechanics are different but in both cases there is a group that has the power to validate transactions and who can collude and steal funds. There is no free lunch.

When you set up your sidechain you can ask the big mining companies to be in your private federation. If you trust them as drivechain validators, you should trust them as your sidechain validators. No need to hack bitcoin and change the incentives of the core protocol.