I think it’d be way, way easier to just dig into the bombard cannon priority orders and copy-paste the information from the Ram line than it would be to create a new stance. Because that’s all Bombard cannons need. Hit Trebs, hit other rams, hit buildings, hit the other things when I specifically tell them to. I’m not certain, but I believe trebs already have this exact behavior and why Bombard cannons don’t is just plainly a mystery to me.
That would be a nice feature to include (it’s just the same thing for the rams but for others units). It’s horrible to have your cannons go trigger-happy on troops or your archers doing a death-by-thousand-cuts on buildings instead of the enemies 2 meters away.
I’ve suggested something similar before. Unfortunaly some people understood it as “auto search an raid and kill villagers with one click”. You have wrote it better so I hope this feature is considered.