Opening applications isn't the pain point for me. Its resize and moving windows. i3wm completely solves this problem already. It would be great if someone ported it over to OSX.
I really like jigish's Slate[1] for this (maybe I'm just too lazy to switch) but sadly it's not being maintained, and I just noticed that neither is mattr-'s fork[2] as of this month.
[1] https://github.com/jigish/slate [2] https://github.com/mattr-/slate