How about the pilot workforce, based in the UK, accept the ID card, once issued to them by, one assumes, a competent authority, on the understanding that a crew member will swipe his/her card through a reader and if 'OK' will now by-pass all other security checks and be allowed to proceed direct to the aircraft?
Thats no different from flashing a passport/air side pass to gain access. Only difference is that if challenged afterwards your biometric details e.g. fingerprints are stored on the card so they can be checked with a handheld device on the spot to see if they matched. Whereas to check the identity of a passport would involve removal of said person to a secure area whilst it was verified externally.