Sorry, I'm a big fan of "all on" or "all off". At least you know where you stand if the situation suddenly goes pear-shaped.
That's the Boeing idea, and generally it works fine. There's always a but. I used to fly B733 in 90's and in an RA it was A/P off. No mention of A/T. I moved to B738 and it was all off. I then checked back with the up to date B733 book and it had changed too. When I asked a Boeing pilot, he repeated the Boeing mantra. I've seen too many low speed events with high level RA's as PF forgot to reconnect A/T and PM was still breathing fast. Low interest to those comments.
On finals I'm not a fan of anything that reduces PF's involvement with manually manoeuvring the a/c and dulls the loop of PF-aircraft hand- eye coordination. Derfred has a good point. Don't encourage PF to reduce their scan of what's going on. It is not a playstation and needs positive control of all parameters, and speed is one the more critical. The pilot's brain must be well ahead of the a/c and therefore sharp & alert.
How many operators make A/T mandatory for LVO approaches? Some do. It's not a Boeing thing, but if airlines begin not to trust PF's skill in maintaining speed in manual flight, they might carry that across to auto flight, unnecessarily technically.
There is also the case to consider of not allowing pilots to operate under conditions that may be allowed and expected under MEL guidance. A u/s A/T is not a NoGo, and it is a single system i.e. no back up. If crews are not used to it being off, but are then expected to operate a whole flight in manual thrust, it might prove a little too much for some. We've seen the consequences of mollycoddling pilots in too much automation. Considering my early days in B732 and last days in B757/767/738 I've seen a wonderful evolution of automatics and enjoyed many of the improvements on offer; and never felt I'd lost any control. What did make me feel emaciated was mollycoddling SOP's.