I have done that(though not successfully lol). I like playing co-op, keeps me away from the unbalancing matchmaking... and the way I play it keeps it fresh to me, I can guarantee that anybody else who plays co-op seriously like me has used even half of the setups I have.
Regarding Competitive, you can always try Fragged Nation... although I still consider the Shade scenario way more challenging (no one has accomplished it).
I'm not, I just brought up the things that are more important than partysplitting. Then you came along saying partysplitting is the biggest issue ever and nothing is more important!
I'm fine(not in the sense that it's good, but the sense that I'm dealing with it) with matchmaking and still have fun both with/without my friends in uncharted but playing lone wolf and with varying party sizes it is easy to see the problems with matchmaking and the issues overall with it...my smallest concern was with partysplitting...
What is more important than party-splitting then? Party-splitting IS one of the biggest issues in U3.