So basically, we want a bunch of attack speed and critical strike on this guy, with a little bit of AD mixed in there.
So, a build like:
This gives him 110% critical strike chance, 175% attack speed, and 90 extra attack damage. Im assuming here, but if he gets 1% extra attack damage for every 1% critical strike chance and 1% attack speed, thats 285% increased attack damage, making this give him 346.5 attack damage, excluding base AD. Average ADC base AD is around 100 so that,s about another 385 plus 346.5, so that's about 731.5 attack damage, rounded to 732. That's a LOT of attack damage. Then again, he will likely be shooting a little bit less than once each second since he can't gain attack speed or critical strike every attack, just every 4th attack. That 4th attack will hurt like hell with Infinity Edge... likely.
He also gains movement speed per critical strike which I'm not even gonna try and calculate. If he does it right, he will likely be getting the 4th proc and then going super sonic speeds for a short few seconds. I personally can't wait to see how this works.