didn't have time to check the replay :
but the pr about target priorities is this one : https://github.com/FAForever/fa/commit/0891e455f5845ed62104a32ef24cfe72b6ae65b8
petric did change some stuff here, but shouldn't have any impact for what been reported : https://github.com/FAForever/fa/commit/39f5b3291a77f02fdd7cf1dc45f8d32117bcb796
target priorities on the fly should work (with unability to change target on the fly to the ACU unless unit have the category 'SNIPEMOD').
As for pillar not retargeting automaticaly to T1 unit, it works as in the code : It always has been the same, it's priority is to shoot mobile unit. ACU doesn't have a lower priority than the other mobile unit, so it won't retarget. I guess it can be change, if wanted.
For percy its target priority are T1<ACU<T2<T3