Don’t fly the 139 either, but as has been asked before but does the RFM (or even Leonardo directly) state a height above which the OEI trg switch must be selected back to normal? What trg benefit is there to be gained by keeping it in OEI above that height all the way round the circuit to the final approach? Once any profile has been flown, diagnosis done and first set of ECL actions completed could the OEI switch not just be deselected? “Continue with the rest of the checklist as if still OEI, but I’m just going to reselect AEO, ready, 3, 2, 1 etc”
You’re not really gaining much climbing all the way to eg 3000’ OEI, all the important stuff is done well before then, by that point tends to be down into subsequent actions, considerations etc. Fly the pattern AEO, then just before top of drop, “no drills required, reselecting OEI for the approach, ready, 3, 2, 1 etc”.