Machaca
"The other is: 1. Initial UAS leading to upset, leading to loss of AP
2. Manual recovery
3. FD bars re-appear
4. Catastrophic LOC due to following FD orders"
Why have you assumed upset caused by UAS?? "First" Upset may have been generated by #4 ?? I think your short sequence is probably bankable. If 447 was occupied soldiering on 3:15 past LKP whilst dealing with UAS, they would have been 20nm past LKP and after things went pear, did they attempt a turn back to Brazil? Or, ......
Now 3:15 of continued flight would mean the "Fasten Seat Belt" was on and alerted, so perhaps another look at the conclusion that recovered victims were necessarily unbelted may be needed...