Same here in Coop.
The most obvious reason for the current state, reasonable Teamwork,
aka a Multiplayer remnant.
If that works, why not? But Coop, is like you mentioned, a retard Bot
driving like crazy. Player has no use, other than in driver Position,
place reasonable, stay when needed, stop where needed.
Gunner position, well, it's the most useless Player/Bot combo position ingame.
For Coop a solution would be fine. Cause atm. Mobile Arty is simply AI only.
Take working solutions like Wespe or StuHIV, same principle mobile Arty,
If Player enters, residing Bots can't mess around.
but not such trouble with Bot/Player interactions, stupid behavior.