Im am currently doing that, playing a game only with the friend i started it with, and since he doesnt want to play DOS anymore, the game hasnt moved since then...and the result is the following: i have a bunch of midlevel characters, some of them are made up with my friends playstyle and for those two reasons that game will never be played again if i have a later save in the game in the soloplayer section.
It may sound selfish, but if you have to start over a new game each time you want to play with a friend, and if you have to be with that friend to go forward, the game will take FOREVER to go on.
The point is that when you join a friends game, OR you are gonna repeat the same things you already did 20 times before, OR you are gonna do some new stuff in "shoes" you have never tried before and which might be not to your liking...
For the part when you fill in your game mate... well, what if you kill interesting bosses or did some gamechanging decisions, as a part of the coop game, if its coop the way you mean it, the selfish person... is then yourself...
