That's a non-starter. There is a legal impediment to that option. UK domestic passengers cannot be legally required to pass through UK border control after a domestic flight. Immigration and border checks under UK law apply only to international travel. While airports or airlines can request photo ID for security or operational purposes, this does not include a statutory obligation to present a passport. Any attempt to force domestic passengers through a border checkpoint would exceed legal authority, could be refused by passengers, and likely result in regulatory or legal challenge. In extreme cases, pax could seek legal remedy for unlawful detention or obstruction!