Like I said, no one knows what sully would have done with direct law on that day.
He was applying full back stick because he tought 9.5° of pitch angle with no increasing tendency was not enough.
But how much did he want ???
With direct law, he would have gotten exactly what he wanted, within the limits of the airplane and physics.
But he got limited by normal law.
That is for sure.
For the rest, you probably know it is possible to dive in order to get some speed and then to pull up to perform flare, many pilots do it on a light aircraft on a regular basis, there is no reason why it would be impossible on a large aircraft.
Even without going that far, most flares are transitory situations in which the runway height has a critical importance.
To be clearer, I mean that in a flare, speed is traded for a rate of descent reduction. So if the runway was 50 meters below, flaring at the orginal height would be.. 50 meters too high.
So it is clear that light or large aircraft, pilots have to fly transitory situations in which they have to precisely assess their height above the runway, so there is no reason why it would be impossible to land at any combination of pitch angle/vertical speed desired, on any aircraft. The only variable will be change in speed, but since the situation is transitory, it is not a problem to see one's speed change, as long as it doesn't do so for too long a time.