I'm actually not sure if KWin can't do those things. The things you mention sound very familiar :D
You'd be surprised to find out how powerful KWin is these days. Tiling, grouping/tabbing, window shortcuts and a huge variety of window- and application specific settings are all easily accessible from a GUI.
Personally I'm quite happy with such settings. On my desktop I don't have much fancy stuff but on my small screen laptop I actually use quite some of these features to use the screen as efficiently as possible.
One that I'm currently missing is to hide the window borders on maximized windows. Actually it's there, in the config file, but it's not in the UI. For those curious - change "BorderlessMaximizedWindows=" from false to true in ~/.kde4/share/config/kwinrc
As you can use shortcuts to un-maximize and tile windows, there is no reason (for me) tho show the window decoration.
Anyway, I wouldn't claim that Awesome has no features KWin doesn't have - I'm sure it does. Just don't put KWin in the same group as Metacity, it's far more capable and pretty much everyone greatly underestimates it ;-)