I like the idea. I dont know about the guard restriction, maybe though.
In terms of the admin load I'm sure it would go up, but you wouldn't know how much until it was tried so might as well try it.
It would be nice if it could be triggered by contraband detection instead of a hook command, though it would be a lot less useful that way.
Another ID that would sort of gut it but make it so it fulfills it's original purpose would be if the command would only make the in system bases hostile. I doubt this is possible because everything around them that was allied would also become hostile but I thought it was worth mentioning.