There's always someone checking on those gates and this lane dragon will discover quickly what you're trying to do. Anyone has to understand that there's some money behind this. Every airport providing a fast track lane is charging something to the airline for every passenger eligible. If they scan a BP of a non-eligible pax and let him/her go, the airline will likely refuse to pay the fee for this pax. So the airport operator has no reason to let a non-eligible pax to go. At the hubs, the dominant airline may have specific arrangements to be more "relax", but that doesn't happen usually at outstations.