all fair points, and I quite understand. I'm not arguing.
I would just say that if anyone wanted to do something along those lines, they don't have to go that far.
Orbats for historical battles will designate artillery reserves to particular formations. Don't allow attachment outside those assignments.
Artillery parks are not deployed for combat, so if they are attacked, they are in dead trouble. You could make up a simple rule for enemy overrunning an artillery park if it actually comes up.
Assume artillery just attaches - there are already rules for 'reserve movement' which is very long, so assume this is something of the kind. After all, the game turn represents quite a long time.
Allow this at the cost of an individual unit activation for the artillery unit in the park, so it's not too attractive an option compared to deciding your artillery allocation in advance. I wouldn't want to encourage gamesmanship.
Once deployed, has anyone ever retired artillery to an artillery park? I just wouldn't allow it, and don't think that would ever be a problem.
Just some simple suggestions. for a historical or scenario game, if anyone wants them. No need to go over the top, as it would still be doing more than most rules even attempt. And I'm not suggesting you incorporate any of them into the main rules, just throwing them out there for players to mull over.