Already know about that design,its efficient if we had 1.7.2 update on minecraft, atm we only have ice block,not packet ice
and if we use allot of hoppers to get the mob loot ,or the obsidian pipe with a combustion engine for max range
But i made some modifications on the current farm, i replaced the blocks where water flow is with the ice for faster flow and some trapped doors on the pads to make the moobs step over faster