I've watched at least one game with Sivir mid. It.. seems like a riskier idea. But then again I play AP Varus in mid lane and he has less mobility than Sivir, and no spellshield.
I think it is possible to get away with, but the question is how you would really fit into the team comp thanks to what the current meta is like. As far as builds, the match I spectated had the mid Sivir using Guinsoo's Rageblade. At first the Ability Power seems like a waste, but her Q actually scales from both AD and AP and the passive would be great for risky trades if you knew what you're doing. Versus Youmuu's... typically, that isn't thought of as an ADC item. The thing about Sivir is that once she has her Ult, her W becomes a steroid, so the active might be redundant. But I could be wrong, it might actually have good synergy with her kit in that way.
If it works for you and there aren't really any better items, keep using it. Just make sure that you're not wasting an item slot and could be using something better.
Bottom line, though... Sivir Mid might be something that takes a lot of practice and skill to get to work. I think it's possibly a holdover from when the meta was older. Going even further back, Ashe Mid was evidently a thing once upon a time... so who knows.
is fantastic so far- gives Apen on her Q, which I think I should max first. Rest, idk?
