One operations manager's objections can be summarised as "There is less clarity around pilot flying and monitoring functions when there a handover of control. Hasn't that contributed to several incidents throughout aviation involving an unusual attitude or loss of control at the bottom of a IFR approach?"
In fact if compared on an exact like-for-like basis there is usually MORE clarity about who is flying and who is monitoring when using a PicMA procedure. The NTSB pointed this out in its 1974 study. It noted that a transfer of internal and external monitoring duties is called for in procedures without a transfer of control (i.e. traditional PF/PM procedures), but not in PicMA procedures. This exchange of monitoring duties is far more hazardous than a planned exchange of control.
The NTSB recommended that to ensure the essential continuous monitoring of the aircraft's instruments from the OM to landing, the wording of monitoring tasks should be specific. Procedures which involve a transfer or exchange of visual scanning responsibilities (i.e. traditional PF/PM procedures) should require that the appropriate crew member announce that he or she is relinquishing previously assigned duties or responsibilities.
In addition, procedures should limit sighting call-outs to those visual cues which are associated with the runway environment, and un-required callouts which can result in the premature abandonment of instrument procedures should be prohibited.
Few if any operators comply with these NTSB recommendations in full.
As far as multiple occurrences of "unusual attitude or loss of control at the bottom of a IFR approach" resulting from control handover is concerned, it has not been possible to find any examples of this in an extensive literature search. This concern appears to based on hearsay and rumour, not fact.
Accidents and incidents involving control handover have almost invariably been the result of UNEXPECTED handovers when it had been intended that a First Officer would do the landing. Either the Aircraft Commander has belatedly taken over, or the First Officer has abruptly relinquished control, because what he or she perceived to be an unsatisfactory situation. The two factors of the situation already being unsatisfactory, plus a completely unexpected reversal of PF/PNF role, can indeed be catastrophic. But neither of these factors is present in a PicMA approach.
What is true is that there have been many instances of loss of control or unusual attitudes at the bottom of "traditional" IFR approaches, usually as a result of the Pilot Flying being unprepared for a go-around. This has applied particularly with modern automated aircraft. The probability of such loss of control is significantly reduced by PicMA because the copilot is fully "primed" for a go-around on every approach.