Why would I read your entire post when you want people to use a terrible weapon in a way that makes you an easy Sniper target for only a chance to disable a sentry so your team can maybe do something about it, when the Direct Hit is a thing.
The Cow Manger is best used for trolling, or MvM, its alt-fire ability is trash, and the window that it gives to you to do anything to a disabled sentry hinges on the rest of your team being around in that 1.5 seconds while you furiously try to reload, and that's only if the other team's Sniper(s) let you fire your charged shot that leaves you an easy target in a Sniper sight line.
The very fact that you say that you're a Soldier main, and advocate the Cow Mangler for buildings, leaves me to believe you are a shit Soldier.
Edit: I'm not entirely sure that the Cow Mangler alt-fire projectile is immune to the Short Circuit, either, considering that it can be airblasted like a normal rocket. I've never tested this theory, as I don't use the Mangler on buildings.