A little attention to one of the forgotten "hyper carries"

I read an interesting thread someone made about our favorite little voidling . He/she said that if there was any champion who should have true damage it should be kog'maw and that gave me a pretty nice idea (except when he dies). It's still confusing why a ADC should have a passive which only works when killed when the point is to peel champs like kog. But that's another topic.

Anyway, I used to play Kog'maw as my main ADC for some time ago and there was one thing that bugged me all the time. How much of a lackluster kog's Q was. It had very low range so the active was never used and it was more of a passive AS-boost. Then Riot finally normalized the range of the spell and changed the flat armor/mr shred to percental, making this skill waaaaay better. But i still feel should need some buffs because does almost the same job as kog but being much safer pick in both soloQ and ranked team due to self peel, when kog has none.

Today the spell says: Caustic Spittle PASSIVE: Kog'Maw permanently has bonus attack speed.
ACTIVE: Kog'Maw launches a corrosive projectile in a target direction, dealing magic damage to the first enemy it hits and reducing their armor and magic resistance for 4 seconds.

So then i read the thread saying that adding true damage to kog's kit should fit our little fellas kit as the true imobile tank-buster. Mythought on how to add this was to change how Q works with W. My idea is:

ACTIVE: Kog'Maw launches a corrosive projectile in a target direction, dealing magic damage to the first enemy it hits and marking them with "corroded armor" debuff for 4 seconds. Enemies marked with corroded armor takes 50/50 true damage/magic damage from bio-arcane barage (not scaling with ap on the marked enemy). The number can be changed but my point is to have some kind of interaction between kog's Q and W to add true damage.

Just my 2 cents on how to make him more of a true tankbuster and strengthening his niche.