I had the idea that units would only shoot at units they were designed to be shooting at:
A long time ago I wrote how it irked me that infantry shot at tanks which they can not harm, snipers giving away their position by shooting at SU85s if not on hold fire Maxims firing at Bunkers which they can not deal damage to etc.
And vice versa I would like to have armored units shoot other armor and ignore infantry. That only the hull MG and top gunner auto-target infantry. Only if targeted by right clicking or via attack move the tank would engage infantry targets.
Now you could argue that this would be more micro intensive, but wouldn't it be more rewarding? That your Panzer 4 turret would only turn if armor comes into range and not every time an engineer comes out of the fog of war for 2 seconds? That the Pak43 and Pak40 would be silent until a proper target comes into range not alerting the enemy to its presence? StuGs and SU85s not being able to decide which infantry to shoot and then being flanked by a tank that comes from the opposite direction? Though this is of course a practiced tactic, to lure the AT tank with infantry, but ATM we are using the units AI that tells it to shoot at everything that comes into range. Without the auto-targeting of infantry the tank would just sit there and maybe fire its turret MG if its a StuG. but you would have LoS with your infantry and see which way the tank is aiming. Now you can still flank it. you just have to be more careful with the approach.
Though with right clicking (or attack moving or shift+right clicking) every infantry unit you have to micro a lot more. It comes down to how useful and worthwhile the not-shooting-everything-on-sight will be compared to the more clicking you will be doing. I think it will be a good thing to have have more control/responsibility over your units.
TL;DR: Infantry should not shoot at tanks and buildings it can not harm or destroy. Tanks and AT guns should only shoot at tanks, not at infantry, unless the player specifically right clicks on them or attack moves with the unit.
+1 To the 4 man Pak43 crew unless it includes further problems with the upkeep.
+10000