Once again, as I slowly come to ways to be able to condense my reasoning for this, I will repeat why this is a bad idea.
Most AP users are Burst, outside supports for the most part. Most AD/Tanks are less burst, or at least in the early game, require more time and effort to be able to kill things than AP folk. Requiring that time to be longer, they need GV earlier in the game, because Healing beats DPS, but Burst beats Healing. If you kill them in one go, they can't heal from it. DPS needs to whiddle down the constantly healing champions like Mundo or Olaf, which is their items are cheaper.
GV should be locked behind an expensive item because the ability to massively burst people shouldn't also mean that you're also able to stop them from trading with you at all. If you can't kill them with your combo, they should have the opening to replenish their health and continue to trade early game. This doesn't apply later in the game, where healing is far more than just base numbers.
You shouldn't get both of best worlds early for GW and Burst. You shouldn't get a higher ability-to-kill percentage of their health, but also get to negate any way of them being able to deal with that. It becomes considerably one sided. AD/Tanks get that because most can't kill you from 80 to 0 at level 6 in a second or two.