Some random thoughts:
An idea to use a multi-FSS with those multi-talented guys (LB James, Billups, Nash) would be to have the regular buttons do something extra when the mod button is pushed. The way I'm thinking of this might be hard to explain, and it might not turn out to be that good of an idea, but I want to say it so here it goes:
[I'm using a PS2 controller and I use L1 + Triangle(powerhop), Circle(shoot), X(pass),Square(layup/dunk)]
Push L1 and Triangle, you get a FSS power move down low
Push L1 and Circle, you get a FSS shot,
(if you are behind the arc, its a tall jump shot for 3 or a fade-away)
Push L1 and X, you get a FSS pass,
Push L1 and Square, you get a FSS dunk or layup.
What if the player you are controlling doesn't have a certain FSS?, or none for that matter?? Well it just does the normal function. This could help because it is not confusing, you know what each button you are pushing does as a function even if the player isn't a FSS.
-Obviously there would be a couple of flaws with this, one being that I'm not sure how you would choose which Superstar move that they do, (like when I push L1 and circle behind the arc, will it do a high jump shot or will it make the player fade-away. Maybe the computer can decide which move is most appropriate - although this seems like something the user should be in charge of...maybe it could depend on if the user is holding the sprint button or not ? )
-Possibly these players can only do these really cool moves once or twice in a game, because really how often does it happen that Carter does a disgusting dunk. At most twice a game, and that's lucky. Maybe restricting the ability to do these dunks would lead for the solution above to be a good remedy, as it could randomly select a dunk that hasn't already been done yet in the game (on both teams?), therefore making it not important that only one button is attributed to FSS dunking.
I think a guage could be implemented as well, based on turnovers, field goal%, or some indication of good play. This is so that you have to earn the FSS. I think restricting them is good too, because if you see them too much, they become less impressive - but only seeing them once or twice a game, people might actually be shocked at what just happened and maybe they'd actually use that FSS replay function.

. How would the gauge work? I think a simple way would be that it is just a bar: a good play fills up the bar partially, a bad play takes away from it. Once the bar is full - LOOK out, then you can do your FSS. Now another thought on this would be: Does each team have a bar , or does each player have their own bar. Since I'm just imagining all of this ridiculous stuff anyway, I'd say each player could have their own bar, depending on how they are doing that game, it fills up and they are able to use their special skills.
Another random thought I had for FSS was for the Playmakers:
FSS sucks for playmakers right now, IMO - if a player has an alternate FSS than the playmaker, I always turn it on. Because I use direct pass all the time anyway, which means I don't use the FSS with the playmaker.
-I think using the direct pass could easily be incorporated into the game for Playmakers to take advantage of, in that whenever I use the direct pass, lets say from PG-Nash to C-Amare [I think for my control settings its L2+ ProHop(triangle)] it does a cool playmaker pass. Maybe the way the ball is passed could depend on how the player is being covered. If Amare is posting up, Nash would give a higher lob pass to him, rather than a more straight (chest to chest) or bounce pass that could get picked off. Or perhaps Nash (& all FSS playmakers) would be the only people that would be able to pull of the bounce/straight passes when a player is being tightly covered. Also, the FSS playmakers should be able to do sick passes on fast breaks, or 2-on-1's. If the FSS playmaker is open and on a fast break and you call for him to alley-oop it to his teammate, he tosses it off of the backboard, or behind his back and off his elbow (ala Jason Williams). EA could definitely improve on the playmakers, and make them more coveted/valuable.
Defence FSS:
I think the most recent March Madness had a lock-down function for defending (I played it once for about 15 minutes), why not put this in NBALIVE 07 for FSS defenders? the better your defensive awareness, and ultimately FSS defense, the more tightly the opponent is covered (this is assuming its a man-to-man formation). Stealing should definitely be more about seeing where the ball is going to be passed to, instead of tapping it out of the opponents hands as he is dribbling. Perhaps a cool lunge forward could be one FSS stealing function, but be careful when using it to pick-off opposing players, as it will leave you out of position if you miss.
This turned out to be pretty long. Sorry for that.
I might post more as I think of how it can be improved. Thanks for reading
-S&C