+1 for this answer.There are no special rules at all on the doors, so it is safe to assume they function exactly like the door on other vehicles, which act as dis/embarkation points. Otherwise they are decoration and do not count for the hull of the vehicle (in the same way as anntenna and suchlike), they do not impede movement and do not increase the footprint of the vehicle. Use the main body of the vehicle for measuring distances, template hits and so on. As for the doors being open, it really is up to the controlling player. It is no different to sticking any other vehicle down to block LoS, so I don't see why people should moan about drop pod doors but not that. There are plenty of valid fluff reasons why some/all of the doors stay shut (the marines deliberately don't blow them, malfunction, they shut them afterwards to protect their valuable transport/provide themselves with some cover etc), so people can use them how they want.