It's more like this:
Crit needs to be removed and reworked so ADC itemization isn't this shitty quadratic scaling that causes ADCs to be useless pre 30 then gods post 35 when building crit. Make them scale linearly. Like Essence Reaver becomes an AD mana item with 20% CDR, Infinity Edge increases auto attack damage by 25% (except on hit effects, but does apply to spell onhits like Ezreal Q and GP Q).
For AP itemization, Morellonomicon needs to be nerfed and other AP items need buffs. Candidates for buffs are: Hourglass getting it's active reduced to 90 second cooldown and potentially a bit more stats. Luden's Echo just needs -200 gold cost. Deathcap could use less cost as well. Void Staff needs to be 40% bonus magic resist.
For tanks, I'd nerf Sunfire, buff deadman's slightly (like 5 armor or 50 HP), and rework Thornmail (So it does it's job of whatever it should do. Shouldn't be just an anti-Jax item.)
For bruisers I'd make Sterak's Gage melee only (still procs in the ranged forms of duel-range champions), make sure Deadman's was buffed, then make Sterak's and Maw stack again (ranged champions can't get Sterak's now so..), and keep BoRK good on bruisers not just ADCs.
For AD assassins I'd nerfed lethality to 0.50 + the other 0.50 based on enemy's level, then give Edge of Night a new passive.
For onhit itemization, rework Rageblade and don't give it Phantom Hit. Make it just a normal 3000 gold or so hybrid item. Make a new 3600 Gold item that gives 70% attack speed, 7% movement speed (remember zeal wouldn't give crit anymore, probably AD), 15 AD, and a passive that procs Phantom Hit every third hit.
As for new items, 1 more item to build out of the following:
,
(wouldn't stack with Maw, hell this could be the new EoN, no the shield wouldn't be large like Maw),
, and
.