Flat Armor Penetration

Ever since Riot announced that they intended to change Flat Armor Pen, I've been thinking about how they could possibly change it so that it felt like a stat you would take against tanks. Aside from changing all flat penetration into percent penetration, I can't think of a way to balance it more for tanks rather than squishies. However, I can think of a way to make it feel better for both tanks and squishies: Apply the armor pen after percent reduction instead of beforehand. If you aren't taking any percent reduction, than there's no real change, however, if you do, then flat armor pen feels a lot better against tanks. The only problem is that such a change could be a massive buff, and would necessitate lowered quantities on the items. Which, I suppose, could be a small nerf to killing squishies, but I don't know.

Anyway, I'm curious to know if anyone else has any ideas to what the changes could be, I'm not really satisfied with my conclusion, but it's all I can come up with.

~CrimsonCobra3