Ashling,
Thank you for that google tip; the Airbus submission to the NTSB was particularly interesting, as I hadn't realised that when in alpha-protect the aircraft develops a phugoid. In normal law there isn't a phugoid. So then we have:
There are feedbacks within the AoA protection law aiming at damping the phugoid mode (low frequency mode). Without these feedbacks, an aircraft upset from its stabilized flight point up to constant high AoA would enter a phugoid (which is, by definition, a constant AoA oscillation) without possibility to stabilize the trajectory. As a consequence, commanded AoA is modulated: for instance, if aircraft speed is decreasing and/or pitch attitude is increasing, pilot's commanded AoA is lowered in order to avoid such a situation to degrade.
Trying to run simulation without such damping features on the very last seconds of the flight, without considering what could have been the effect such features brought upstream during the flight on the overall Aircraft trajectory and management by the crew would be pure speculation, as not supported by technical facts.
On the last 10 sec in the air of Flight 1549 , DFDR data show that pitch attitude is increasing and CAS decreasing. Then, the phugoid damping terms are non null and are acting in the sense to decrease the finally commanded AoA vs. the stick command, in order to prevent the Aircraft from increasing the phugoid features.
......
..... with a loss of engine thrust, as in Flight 1549, the aircraft energy management significantly increases the pilot workload. Under these circumstances, aircraft is still able to reach the optimum water impact configuration, but this is a demanding task which requires time and significant pilot focus. Typically, the flare initiation height will be critical to the achievement of the optimum water entry conditions.
Now that means that the features that limited Sully's flare are necessary for stability and that removing them might have adverse consequences on the approach to flare. [edited 26/03]
Also, that last sentence is, IMHO, the key - height of flare initiation is the important parameter.
BTW, the picture I have seen illustrating the various 'alphas' is a schematic with the differences dictated by presentational requirements as much as actual values. I would be surprised if there was much between alphamax and alpha stall - the commercial pressures are too high to allow much leeway when competitors are basing their products on alpha-stall