To expand on what these gentlemen observed:
No, because one who does opt out doesn't care about rank anyway. and those who do care about it won't opt out. 
...
Other potential issues I see with this is channel 200 purse fights about a player's actions and if he did it just to protect his score. "You didn't opt out of the scoring option so every more you make is for your score." Or, we'd hear all kinds of whines about, "I would be a better rank than you but I just choose not to do it it." .
It would provide a means by which to identify and isolate players that play your way or not. And, from what we've learned from observing human nature, once you've identified, en masse, those that differ from your values, you now have a 'common enemy' to rally your 'fellow believers' to berate, insult, humiliate, and cast disgusting looks in their general direction.
Heck, it's bad enough with some of the squad bashing that goes on..
If you think that removing a rank system is going to magically convert a player into choosing a P40b instead of the N1K, I'm afraid you'll be sadly disappointed.
Like it or not, the rank system is a measuring point that people can use to gauge their performance. I can't count the times I've tried different things just to see what it's affect would be on my rank.. kind of like a truffle hunt, I suppose... or maybe that was wumpus? It's a subgame within the game itself. Useful to some, not so much to others. Just like bombers, GVs, field guns, fighters.. Some are more useful ( i.e. enjoyable ) than others.
Getting rid of it will not change their play.. they'll just go by their stats.. which is a bit more of an effort to track.
