Forgive my obvious naivety, but whats wrong with Mode C/S veils?
Surely they help to
- cut down zone infringement through positive identification by ATC (ok, so will never stop someone who's determined to drive through not squawking)
- help reduce airprox and allow suitable routing of conflicting traffic in good time due to positive identification
- enable TCAS to do its job properly when conflicts do get too close
Or have I missed something? (apart from no electrics, ultra/micro lights with no spare capacity, etc... but would they be under the LTMA anyway apart from in known areas such as Dunstable?)
Alternatively, are the exceptions enough to warrent dismissing the idea totally?
(ducks and runs for cover)