Having position: could it be mutually beneficial to swap places?

[phish]

I understand what you are saying and it's an interesting question.
You're gaining an advantage in that you will now have the best position more often than normal. He gains by being to the left of a LAG. But I think you lose a little by having him to your left. Before, when he enters a pot, you can throw you more marginal hands away. Now, if you enter, and he raises, you're trapped in there.
But to answer your question, if there is any gain in EV for the two of you combined, it will come from the person who left the seat to your left and now has taken the seat to your right (it may be a different person).