Something I just thought about right now...
 
Wouldn't it be pretty cool/fun to be able to play with a buddy (adhoc or online) on the same team in the spirit of my player mode.. where both of you get to "upgrade" your skills over time?
 
I just think it would be awesome to have a team with your buddies controlling different positions on the same team.. with custom players :)
 
Hell... would be even cooler to make your own franchise with custom players and compete for the championship xD
 
Can you imagine a GiantBomb NBA Team :D?

That would be cool if you have four friends that you know will be able to play on a regular schedule. I'm not in that situation though. I'd never make use of the feature. 
 
If I'm not mistaken, you can already take my player characters into one-off online matches though. It's called Crew matches I think.