The largest thing I’ve landed at Jersey so far was a 737-300 at about 50 tonnes, so an A319/320 would probably focus the mind!
As you say, GS mini along with the auto-thrust response and gains etc, have probably been refined and improved via software updates since 1988, and I personally have never had any problem with it, (flown it since 2005). A superb and very clever system in my view.
I agree that A320 is perfectly flyable and easy to fly in fully manual. However, the auto-thrust is now so good, (and of course there is no pitch/power couple), that it is not often necessary to take it out. (I know - I’m being lazy !).