The worst case scenarios is that all the users of a sidechain are at risk of their BTC being stolen by miners. So the risk of theft is 'opt in' for the user of a sidechain.

Drivechain allows miners to collect significantly more revenues (or more).

In return, they are encouraged to (but never required to):

…activate/deactivate sidechains, in order to maximize BTC’s price & maximize total txn fees.

…investigate the status of a disputed withdrawal (of which there can only be one per 3 months).

This is precisely what Satoshi intended for miners. Merged mining was invented by Satoshi, and has been in continuous use ever since e.g. Namecoin and Rootstock.