You're right about that, she hasn't been updated. No one is sure what she needs other than a safer recovery. I also agree that many of PM's characters get stale very quickly. I can only use Link, Roy, Ganondorf, and Zelda a few times before I'm ready to stop playing that game. Minus usually lasts a few hours at a time though. More creative movesets.
Yea ZSS is a pretty basic fighter. given her current abilities i don't see much you can add, tho i have always felt she was a little too light. maybe making her a bit heavier might help? crystal flash might be another interesting move, its a fairly well recognized trick in super metroid. maybe allow it to fully heal her by a certain hp per second but be interruptible by someones attack? mean while ofc you can't cancel it once you start.
there are also the special beam attacks tho that would be more for samus. i don't think she needs any more buffs xD