Hmmmm...not the best idea. Think from viewpoint of attacker-he'll must to win at very stupid conditions-starbase, golans,other stations, defence fleet and now this planetary guns. Increasing thier damage may be a serious unbalance. Let's don't touch them. I think they're good as they are now. BTW empire magnapulse cannon uses model of planetary turbolaser that could blow ISD in one shot, lol. But we can't put all SW weaponry stats to game, unless somebody wants that single shot from planetary ion cannon could disable any ship for entire battle time :