No argument about it opening up some concepts, but would choosing negative energy/dark still include a tohit debuff, or sonic a -res effect, for instance? You may need to adjust the tiers of certain powers as well, so you couldn't take all AoEs, or take multiple fast animating hold attacks, (ice blast has 2, but the 2nd has a much longer animation, while, if going by the strict arrangement the sets currently have, one could take freeze ray and abyssal gaze to circumvent this).