A Champion Idea Based on Pre-Revert Kog'maw's W

So pre-revert Kog had me thinking : What if his W was actually an ultimate ability on a champion? As amusing as a mini slime-loaded gatling gun is, I think the ability should be saved for a different champion. Not so much the percentage health damage part, but the doubling attack speed part.

This champion would be an robot riding AD Carry with a super weak early game and a godlike late game with his ultimate. The champion would be tankier than most AD carries later on, but completely immobile when using his ultimate.

Here are the exact details on the ultimate.

• The champion roots himself into place,
• The champion gains double his/her attack speed and 400 range
• Every single auto attack is line skill shot and deals 70/90/110% of his/her AD and can critically strike (For maybe 200 or 250% damage).
• The champion can use their abilities while in their ultimate turret form
• On-hit effects do apply (balanced by the fact that you have to hit your shots and the fact that crit is probably better anyways)
• Runaan's Hurricane would create 2 additional streams on each side (Like a spreader power-up in a top down bullet hell shooter), but deals instead 15% of 25%.
• The champion auto attacks as long as you are right-clicking but the missiles travel in a stream like a slightly smoother version of Vel'koz's ultimate.
• It lasts for 7 seconds 0.5 second cast time
• Has a long (200/160/120 maybe) cooldown and can be canceled anytime refunding the ultimate's cooldown based on how many seconds are left.

Pros : Godlike DPS, can hit units from FoW and unbeatable teamfight presence. Cons : complete immobility, long cooldown and heavily reliant on teammates, items, and the teamfight actually starting.

Other abilities in this champions kit could involve a shield (Like braum's) but doesn't last as long. A steroid that functions like Runaan's hurricane and stacks on top of it potentially creating 5 streams of bullets but deals similar damage to Runaan's. And finally, a damage ability that has functions as spam-able artillery to help finish off fleeing opponents or poke down champions before a fight. The concept could use more development, but I'm actually working on a different champion concept. This idea was more or less just a shower thought that could be made into something much bigger.