If people are so concerned about a pilot leaving the flight deck in the cruise for a personal comfort break and even dare to engage in having a tea/coffee and chat with cabin crew then why not have three pilots on the flight deck or even four?
This would mean pilots could get a proper rest break especially on a long duty day.
Add to this bunk facilities for inflight rest on all flights.
I'm sure the passengers and the airlines would be quite happy to pay for an extra level of safety.