Pretty nonsense stuff really...
Not condoning travel ex UK in a National Health Emergency at all but what would happen to the many passengers who may well be denied entry into the destination country then under those proposals?
The onus is on the UK & populous to handle it`s own Lockdown Emergency within its own borders & not to export it & for everyone to act responsibly surely.
So you are quite happy for leisure returnees then to be liabilities of the UK taxpayer & drain too very limited resources to monitor them after irresponsible travel.
Did you ever travel to East Germany?