Good ideas, but my guess is the pilot still going to need to see to taxi out to the runway.
On the right track, but much too extreme.
The door. There's no need for a door between the cockpit and the passenger compartment. Give the cockpit it's own bathroom, its own exterior access hatch, and I guess maybe it's own little food locker. Flight crew and passenger service crew could still communicate via intercom, and maybe even an old-fashioned voice tube as backup.
Someone might still attempt to hijack a plane by taking and threatening hostages, but they could never control the plane themselves.
This wouldn't completely obviate the need for passenger and baggage searches, of course. Bombs would still be a threat, and you'd still want to screen for firearms. Lesser weapons would no longer be much of a problem, though -- One could no longer do any more damage with a knife on a plane than one could on a bus.