If the dropship has blind spots, enemies should be unable to start in those blind spots.
There's design room for craft with a higher capacity but not more interior space, if a soldier in very heavy armor takes up more than one soldier's worth of weight but still fits in one tile. That could also be used as a balancing factor and allow heavy armor, robots, or vehicles to be better, if they take more weight.
Few aircraft are limited in passenger capacity by how many seats they have; aircraft limit how many seats and cargo space they have so that they reach their full load when the seats and cargo bays are full.