Whether or not an outsider could do this - you must first ask yourself: How many times has it happened in the past?
Take the last 25 years.
Consider how many commercial flights (twins and above) that there were on average at the beginning, middle and end of that period.
Now do some basic multiplication.
Now find out how many times one pilot has been incapacitated.
Now how many times have TWO been prevented from operating?
Off the top of my head, I would say: To the first - less than .01% and of the latter? Zero.
On the actual flying ... having sat in the jump seat on a number of occasions, I think that the things that will catch you out are the wind - those sudden eddies and changes and that it all happens VERY FAST indeed.
Now the professionals can give their opinion!