@Riot: What's the reasoning behind giving Rumble an ammo system?

Granted, I haven't played Rumble as much as I should, mainly because if I am looking for a mage fighter I'd prefer someone that can go tank atop of it (Read: Maokai, Galio, or Singed). However, what got me scratching my head was the reasoning behind why there was an ammo system being made for Rumble.

It seems more like a nerf to Rumble since the timing to get his e is longer (2 seconds longer, to be exact). Not to mention Rumble's Harpoon was already specific and is already balanced, so what's the actual thought direction about it?

Also, I've noticed a long time ago that Rumble had received a Shield buff on PBE, only for it to be removed. While understandable for it to be reverted (as that would make his overheat shield rather ridiculous), are there any ideas of stat checking or stat buffs soon to be placed on Rumble? And do you believe Rumble is in a healthy spot given how heavily sided top lane can be in this current meta?

I'd love to see Rumble still hold relevance, but I would hate to see him disappear off this meta, or just be irrelevant entirely in this meta. It's such a shame as well because of how many mage fighters there really are that don't very well excel top lane versus most top lane picks besides tanks.