FD - now I see there was a misunderstanding
As you said flying an ILS with TRK and FPA guidance modes active on FMA (i.e A/P ON) would be a stupid idea (or HDG-V/S btw), but CONFiture and I were referring to flying an ILS with the bird (FPV) without A/P.
Your posts are interesting.
As for the momentary drift of IRS: I think the drift is anything but momentary.