i not shure what this mod should be called but..... anyway like in ouendan/eba multiplayer it would be cool if osu had a mod where when you get a certain amount of combos the screen starts to shake and the markers get incredibly tiny.
though it was posted in General (gj Lolginer) so I can understand why you may not have found it through a quick perusing/search if you restricted yourself to the Feature Request forum.