Overall a bad idea. When Yi goes ap he simply needs to get alpha strike off and use zhonya's or meditate until he gets a kill/assist; granting him a reset. Rinse and repeat. If Alpha strike doesn't deal enough damage because you're not building enough damage, you're most likely going to die before you get any resets or you can simply be ignored completely.
AD Yi is a splitpusher or he tries to kill AD carries almost instantly. Due to his lack of utility (seriously he has none) he's easily ignored if he doesn't deal much damage.
While you can do it, it seems like a bad idea considering he can't be played Mid then and a top Master Yi is so much more inferior to anything else there. Right now, as it is, the only viable Master Yi build is Ap, but you can play him a little bit tanky I guess.
You should never build Rylai's Crystal Scepter on Yi or even RoA. Simply because Yi is a snowballer and if you build a early RoA, you cripple your Early/mid game. The only defensive items you should build are Zhonya's Hourglass and Abyssal Mask.
AD Yi is a splitpusher or he tries to kill AD carries almost instantly. Due to his lack of utility (seriously he has none) he's easily ignored if he doesn't deal much damage.
I think those could be added. The problem is there aren't many AP + Armor items other than Zhonya's.
I guess an alternative could be your basic
Maybe stuff that give armor/MR and AP?
Didn't play too much with AP Yi :P