I would LOVE to see the range increase and the Ricochet on-hit effects... though make it work like Luna from DotA. Seriously, some things could just get out of hand... (Tiamat Sivir ftw!!!)
Her range is pretty pathetic, and does need to be upped, that's a definite thing. Lifesteal should apply to all ricochet hits IMO. CC-like "Orb-effects" (As it's referred to in DotA) shoudln't do that, like a frozen mallet. She'd be WAY too valuable for a team fight IMO. Black Cleaver I'd be okay with. Just stuff like that.
Personally, Especially since the Q nerf, I don't actually get her Q. Call me a noob for it, I've had enough fun with game swhere I've literally gotten over 700 creep kills (granted, the game was an hour and 10 minutes... but still, that's a very high amount of creep kills) because I maxed out Ricochet first, spell shield 2nd, and didn't even touch my Q till I had to. Pushing is awesome, lane process in hilarious (TF: I shall activate a gold card, and approach you with it. This card plus my stacked deck shall chunk thy hp! ... Sivir: AHA! I retaliate to your harassment by pressing E, and continue casually auto attacking your creeps. Little do you know, you're still being hit! I reign victorious!) etc.
Btw, sorry for so much DotA talk in this, even though this is LoL. I'm pretty sure Sivir was at least loosely based on Luna, so I might as well bring her into the equation. And for those who don't know, "Orb-effects" are any sort of item that effects your auto attack to do some kind of extra effect. Some were also called Buff Placers. Lifesteal was an orb effect, as auto attacking gave you life. Slows were both Orbs and Buff placers, as it placed a debuff on them that strictly happened with your auto attack. Black cleaver would work the same way. Starks would be a Buff Placer only, as it's not specific to your auto attack, but to the auto attack of anybody nearby. (I think) Difference is in Dota, you could only have one orb and one buff placer =P