Good idea to re-tweak armor pen items!

Let's be honest, right now the meta is enforcing items like onto marksman and assassins because their items are designed for armor shred. Something like armor shred and armor penetration is really hard to counter, as to devote an item to stop it would ruin other carry's potential to try and itemize against it. The items themselves are also highly cost-efficient for what stats they give, since having base shreds for early game is far better than critting early game on a reliability level, and having an item that can shred %armor late game with the same effect early is just as good. Not to mention their high-base stats, as well as the easy access to cooldown reduction, and the items reign superiority over traditional marksman items.

However, what I believe can be done to make the item balanced is pretty simple: Make armor penetration ramp up per level.

Say right now Youmuu's were to get this change. It would start at a base of 3 armor pen, and level up 1.5*champion_level. At level 9, the item would scale to 17 armor pen. At 18, the item would be at 30 armor pen, keeping itself scaled and relevant by late game, as by late game enough leveling stats have come into effect that armor pen would be nullified due to growths. It would also hit the problem of snowballing from being too spastic in the beginning when it comes to most AD-reliant champions, as it would give them an item of investment with not much gain early apart from the base stats of Youmuus. In a way, Dusk can be affected, as well as , as a per level stat, such that it doesn't become oppressive as a tool early, but more powerful of a tool later. Otherwise, the niche of +base armor pen falls off come into late game, and the item which gives good stats can't be found else-where efficiently, so the champion in a sense gets cooked into having to use said item.

This change would also make the current toxicity of the item in the bot lane be less threatening: if ADCs have to invest in getting an item like it, they would have to be constantly snowballing their lane in order to keep the item relevant, otherwise most growths match it and the armor pen cancels out.