takata/PJ2
Respectfully, a trim function would have more relevance to "upset".
At 2 +/- degrees, a down trim to "zero" would have a steady and insidious
effect on stability relative to airspeeds. With a fault as addressed in the pre-AD testing, trim wouldn't be correctable, and/or noticeable to pilots or computers wrestling with Unreliable a/s data to begin with. Only a few hundred feet (Qantas) can produce a substantial increase in speed. Any established descent, left alone, could be disastrous at flight limits experienced by 447: high, hot, and heavy.
It isn't necessary to impute any other entry to the Sea than BEA's, following an overspeed recovery. Seven miles of altitude to "recover" in, (Assumed). A high speed recovery in Direct Law wouldn't cost a bit of Elevator, VS or other control surface?