@gregsie@snarfed.org@snarfed.org they're already doing the right thing from the start and exceeding expectations, offering any such feature is totally abnormal for a bridge.
Maybe you should consider whether you're doing the right thing by coming into the fediverse with assumptions that bridges should be opt-in when in the community they've always been automatic, opting out purely by blocking.
And in regards to the GDPR (A) nobody outside of a GDPR country cares (B) GDPR applies as much to bridges as it does to other instances, if it's illegal for the bridge to operate then it's also going to be illegal for multiple core AP functions to operate as well.