The first two rules are there for balance reasons. Otherwise there'd be almost no reason to ever buy a powerfist or shoot an HQ with a missle launcher instead of with a plasma gun. Also the partial hits are there for a reason. They simulate shrapnel very well. The not seeing through the trees is the only thing that I can understand simply because it makes sense. The worst "house" rules I've seen was that size 1 terrain blocks LoS to all models. I picked up and walked out on that game when my opponent insisted that a line of barbed wire blocked LoS to his land raider less than 3 inches from a multimelta dread. It's the only time I've ever not played a complete game.