Could we get support for "holding down" QWER buttons?

Sounds derp, but let me explain.

Let's say you're Amumu jungle. You're at blue, and when it spawns, you immediately AA it once and then E for Tantrum. You continue to AA it, and you watch the cooldown for your Tantrum, and as it gets closer to being back up (i.e. 0.5 sec), you HAMMER THE E KEY MULTIPLE TIMES to make sure it goes off again as soon as possible.

Or let's say you're Lux or Gragas. You throw out your Lucent Singularity or Barrel, with the intent of detonating it IMMEDIATELY to either harass or blow up 3 creeps. You press E to choose it, you left-click where to throw it, and then you HAMMER THE E KEY MULTIPLE TIMES to make sure it blows up immediately.

Why can we not just... hold down the button, and the spell will go off the exact moment that it's up?

To be honest, I would probably still hammer the key, because I'm so used to doing it, but let's be honest: this game should already support this; I actually see no reason that it doesn't already. Thoughts please?