I asked this before and it isn't an option. If I've done it right there is a link to the thread here, which will save Andy the trouble of telling you what he told me :
Thank you.
I would have to accept that passangers always happen to be sitting in wrong order and those near the exit have to get out to exchange seats with those that need to disembark first. Just like in a crowded bus where I have to step out to let those behind me exit at the bus stop and then I can get back in.
It is rarely for me to cause opfire by unloading, The point was rather an inconvinience of loading every riding team back to vehicle at every stop when I want to drop off only that sniper.