I think making players anonymous and ratings hidden would help with these situations. Who necessarily knows who the weak player is then?
seating by rating

Well, It doesnt have anything to do with rating. when I play with fukadzume and we are opposed, we DESTROY the poor players who are seated on our sides, espicially if the poor guy tries to go and do the early queen startegy... It doesnt have anything to do with teaming, its just in our mutual interest to do so. I know he will understand the tactics I feed him and he knows I will get the tactics he feeds me, so we can take advantage of that. It doesnt work with evryone, many 1600s and even 1700s play an ultra passive style and avoid all tactics. Which I find boring.
i've seen strong players opposite another destroy weak lateral opposition several times now. friendly queening and not hesitating to open up a weak players king.
let the weakest player move first?
in team version i think the strongest and weakest should be paired.
in the all vs all it would also be a good idea. if the player opposite you goes out you are often in a very bad spot. this makes him more your partner than the other 2. balancing pairings could provide for more equal games.
having a strong player to your left is the scariest. player 1 strongest -4 weakest, i would seat them clockwise 1-3-4-2 so that 3 doesnt get 1 to his left