Believe me- if you have more than two skiers, all the ski gear is going to occupy at least half the back seat area anyway. I don't think you can fit four pair of skis and poles through the passthrough. Two is pushing it.
Three is the most people this car can practically take skiing without a roof rack...but if you have that you don't need a passthrough. Even the boots and clothes for four would be tough to jam in the trunk- especially if you have a spare tire back there, since most winter tires aren't available in runflat.