I totally get where you're coming from. A lot of my challenges with franchises in the past have had to do with trying to match how a player "should" play based on real life instead of his in-game stats.
I wish I could use other teams and still have as much fun, but it never works out for me when I try it.
The more fictional players brought in, the better the game gets is an ideology I wholeheartedly agree with. Not even just gameplay, I get super attached to these guys since they're "my guys" and my guys only. It really enhances the immersion for me and by that point, it really doesn't matter what team you started with anyways.