> Is a justified violation of the rules still to be considered a violation

I think this is key. Having a tank, even if it is nonfunctional and being used as a war memorial is still a vehicle and should be banned unless an exception granted.

Otherwise you'll end up with a hundred "tanks" in the park because they are "allowed". This is one of the things that people who want to slash red tape don't seem to get. Just because it was difficult to get one going doesn't mean that we should cut the red tape. Perhaps we don't actually want/need 27 instances of it.