Bob,
I am with you on AD-ENG-4. I cannot understand any benefit to aircraft owners if this was repealed. I think the dogma AOPA are on re Australian unique ADs misses the point in this case.
I do believe though there are LAMEs out there who would sleep better at night if AD-ENG-4 was repealed. As they sign out for another year an engine that may or may not go the distance some wonder who is liable if the engine fails in that period.
Cheers
TH