Hi there folks,
I'm not really sure what to expect here, so I'm just going to rant for a bit.

Foremost, in the generally agreed upon meta, there are five unique positions--solo top, ap mid, bot adc and support, and jungler. Given how often that the mid is AP, counterpicking has become a common theme, circa de assassins such as Talon finding their way to mid lane. I'm curious how something like Sivir would do mid-lane, given that she has a very early edge on the ap's, especially given if she takes her shield at level 2 she can spam that Q like there's no tomorrow. I understand that this would invite early ganks due to her lane pushing harder than most lanes, but I feel like given what I've seen Sivir do lately, and how often her farm gets robbed on bot anyway, it might be a good idea to call for a lane swap here, as in for the meta.

No, she doesn't have any natural blinks/jumps/gap closers aside from her ultimate, and quite honestly, it's not enough to catch most targets in my experience anyway. With that said, an emphasis on a truly AD focused mid lane could potentially be terrifying. Sivir has terrific zoning potential, and could probably even scare off a Talon or two if she hits her shield like a pro. Now, I'm not saying that this is a good idea for just any Sivir, it would have to be one with a good bit of experience, but if what I've been watching is for real, Sivir, despite a lack of CC, could be the un-counterable counter pick to mid lane, if a surprise.

If I had to give a potential build for her, I'll list what I think might work.

Skills-- 1.) Q, 2.) E, 3.) Q, 4.) E, 5.) Q, 6.) Duh., 7.) Q, 8.)Q, 9.) E, 10.) E, 11.) Duh., 12.)E, 13.) W, 14.) W, 15.) W, 16.) Duh., 17.)W, 18.)W
Reasoning-- Your Q is your damage, your shield is your threat. Every chance you get to hit your opponent with your Q it should be done, any time you think you have a sure fire hit with your shield, use it. At max level, your shield is essentially spammable, and since we're making some CDR, they won't like using skills on you at all. Your W is useful, but it's not something we want to pick up early, and it's not as useful as your other two main skills, and pushing is not our desired goal for this.

Start--Sapphire Chrystal and two health pots
Reasoning-- spam that Q more, expect to take some retaliation, zone like you mean it and back as soon as you have enough for boots and, believe it or not, a tear of goddess, and a tiny bit of spare cash.

First back-- Tear of Goddess and boots, more health pots, wards (duh)
Reasoning-- You're playing her the way an AD caster would be played, such as Urgot, so you need that mana, as Sivir has some serious mana problems if she's not getting hit by abilities very often due to the enemy seeing the counter pick and trying to hit more conservatively. Once you have tear, all of a sudden you can spam that Q all day long and it doesn't really matter. Focus on farming, not killing the enemy, force them to fall behind. Punish them for last hitting, make them use abilities to get CS. Abuse your shield when they do, and hit them with your Q for being stupid enough to get close again. Once you're around 1.5-2k gold, force your opponent to B, or try for a kill, call for a gank, whatever you have to do. Don't let them catch up, go base.

Second back-- Brutalizer, Ruby Chrystal, upgrade boots if there's money, wards (who'd have guessed)
Reasoning-- You're zoning your opponent, and the mid has either called for almost constant ganks, leaving other lanes open for your own jungler to beat down, or he's so far behind it's laughable. This is probably mid game, so by my estimations, you should be ahead about 30-50 CS, pending who you were going against. If it's Talon, he's probably a bit further behind than that, but then since this is theory and not practice, who knows yet. When you're comfortable, go back again. We have many things to discuss.

Thereafter-- As mid Sivir, there are several goals. These goals are, in order, Zoning, Damage, and Ganking. As Sivir, ganking has no hard cc, so if you do try this, go with a team that has plenty of CC. It may be beneficial to try this with a team such as Caitlyn/Ziggs bot, or perhaps swap it up as a clear lane swap when they enter lane, so Ziggs/Nami bot lane, Sivir mid. In this instance, if Sivir ganks a lane with the allied Ziggs/Nami aware of what she's doing, and where she's coming from, the odds of a kill or two are quite high due to Ziggs slow/zoning potential, and Nami having a good two hard cc's. Your main goal is not to push as this kind of sivir, you want your targets completely underfarmed. Never be unwilling to go to town for a teammate, you're not building tanky but you can absorb at least one CC for them.

At the end of the day, you want to have a Black Cleaver, a Banshee's, a Manamune, a Bloodthirster, Berserker Greaves with your choice of enchant, and possibly a Last Whisper, pending the amount of armor they have. No matter who they are, 68% armor pen hurts a bit more than most would like to admit. If they are absolutely face rolling the rest of your team and you can't count on any true help in a fight, you may want to replace Last Whisper with either GA or a Mercurial Scimitar, pending.

For this build to work, there needs to be at least two more attack speed boosts on the team, so for instance nidalee/nunu, due to the fact that this build of Sivir has no attack speed, and relies very heavily on her Q for damage.

Summoner spells can include Flash, Ghost, Teleport, and Clarity. Again, can't stress enough, this is not a perfect idea, and if anyone has anything to say about it, please let me know, I am quite open to discussion on this.

Thanks for reading--Grey