I have been watching this discussion with some interest. I am a boring lawyer by profession but with an abiding admiration for all pilots.
Thanks to a very comfortable income I have been able to spend many hours in both full motion commercial simulators (Qantas and Malaysia) and fixed (737-800 and 777). Additionally I have some hours in a Cessna 172 although no plans to get a PPL.
I spent many, many hours on MSFS using PMDG 747-400 before I first went for simulator sessions with Qantas. A lot of manuals were also read.
For those who doubt the following there are videos to confirm a lot of this...
so with no real world experience (and yes I know it's a simulator) I have undertaken full flights from pre-flight, to programming the fmc, take off, climb , descent, and landing in manual and fully auto mode.
I have had engine failures on take off, multiple TCAS avoidance procedures, terrain avoidance procedures (even in a simulator applying full power to avoid imminent controlled flight into terrain can be interesting), and stall recovery techniques.
No-one was injured in the process and there was no loss of aircraft (albeit occasionally some puckering of the buttocks!).
So my thoughts on the original question posed:
1. Given the stress involved no non-commercial pilot would manage it flying manually
2. Anyone holding a PPL with no prior involvement of simulated heavies would stuggle even in full auto mode given a lack of familiarity of the aircraft systems
3. Yes it is technically possible for a non-pilot to land a heavy using all of the automated help available but frankly in the real world I really wonder!!! Hope I never have to find out!
Thanks lot all of the ral pilots out there.