A point to make on using simulators for upset training in large aircraft. Currently as far as I know there are no simulators where this can be done
I think you are missing the point. Even if simulators had the required fidelity for the full expected range that are unusual attitudes, the problem would still be the instrument flying ability of the pilot. Reading back over many loss of control accidents after the aircraft had got into an unusual attitude, every one was in IMC or at night with no horizon.
That meant the pilot lacked basic instrument flying skills including recovery from unusual attitudes with reference to his flight instruments. One research paper noted that some pilots failed to use full appropriate control movements to level the wings for example. This is discussed in depth in the Maneuvers Section of the Boeing 737 Flight crew Training Manual. For example one statement in the section says: "With airspeed as low as stick shaker onset, normal roll controls - up to full deflection of ailerons and spoilers - may be used".
In most cases the unusual attitude has been the result of poor instrument flying ability by the pilot. All Level D full flight simulators are capable of conducting full 360 degree rolls on instruments. In other words the instruments correctly indicate attitudes flown. It is true that stick forces may not be correctly represented in some simulators but instrument interpretation never changes. Until pilots are taught how to recover from unusual attitudes in a simulator on instruments then loss of control in IMC will inevitably happen from time to time.