The issue should not be 'how difficult is it to fly by hand?' but can the pilots do it? Essentially, in a fbw system, failures of the sort 447 experienced constitute a major emergency. JC makes a very valid point in #624 - is 'flying by hand' actually what happens or is there still something 'interfering' and thinking it knows better? If the a/c, at whatever c of g has been chose for economy, is not safely controllable by the 'average competent' pilot, then either it should not be certified and/or the pilots need to be changed.
As I have said before, all that needs to be achieved by a crew in the 447 situation would be
1) stabilise the a/c at 'onset' level
2) Achieve a safe descent (or climb - if that is what is needed)
3) Make a successful diversion/return
If these are not achievable, then things need to change. Forget AB v Boeing (but do remember which thread we are in. Like it or not, it was an AB that crashed).