This is mainly an "issues" with the tank killer, as it only has 1 ability slot. But being able to change which ability is active, without needing to backout of the encounter and go back to base to change it, would be a nice QOL update.
That way you can easier change between the blast all and the classic 6 volley shot, depending on what you want for each encounter.
#Ability to change unit abilities at unit placement before battle.
worn wind
tribal shale
I think the more pressing issue is why they didn't give tank killer 3 ability slots