Not to be argumentative... placing a heatercore below the hd cage or in the 5 1/4 drive bay isnt a mod. Its like removing the case to put in a cd rom drive. You shouldnt have to cut the case or add on anything. (on mine i didnt) If these are extreme ideas, I believe that you may have given of some wrong ideas as to your requests with that pic.
The stripped off areas are frankly some of your most valuable space for the equipment. Goto
www.svc.com and get some cables that will free up some area. ($15 bucks shipped will convert your entire case with ide cable wiring) Consider heat shrink tubing and/or tiewraps to get the cables out of the way. Hard drives can be mounted in your 5 1/4 bay with a basic conversion kit. If you haven't considered or worked on this to improve airflow in the case i would think that watercooling may be a little extreeme for what you want to do, considering your limiting and lack of desire to spend an hour with screwdriver or moving cables.