The problem is not the map edge, it´s the OOB edge. If I had to cover all those with more statics to make them look "decent" from an arty gunner´s view then I would have to load the map with a TON more buildings, leading to excessive lag.
I guess I will have to test it. I will spot next to the OOBs on different areas of the map and see how the target looks from an arty asset. If testing suggests I will need to add 200 (my rough estimate) more statics then I will just get rid of arty.
Arty might just break gameplay after all, I think there is a reason for not having any arty asset in Battle of Brest for example. It´s a pity not to have any arty in Berlin because it was heavily used by the russians to destroy well-defended buildings.