1) Private Leagues (though supporters get the ability to have more people in them.)
2) Buddy list (that is self-explanatory why I'd want a buddy list)
3) Forum Search (In my opinion, its not important enough to be only for supporters.)
4) Rewards such as trophies, flags, etc. (Wouldn't you want to keep track of your rewards, if you werent a supporter?)
Although I get your point, I just can't see why somebody would like to be supporter if what you have write above were free.
PL is the main reason to become supporter, I don't think most users would like to pay only to have shirt numbers or trophies, so the feature list for supporters should be long and attractive.
Supporter option is not expensive (or at least I think so). You're free to pay it or not, you can enjoy the game with both options.
I can understand that "free" users would like to have more features and perhaps they get it soon (don't know what have the BBs in mind), but at least asking for PL is unreasonable to me.
And as GM PatjeBono said, this thread has another topic. If you want to discuss about more features for no supporters, please go to the suggestions forum. What the guy who opened the thread wanted is to discuss about the gift. You are a very active user in the forums and you know you should respect that