Foot print is not just a determining factor in space Randy, Height is another major concern since personally I would not want to see a big ugly skimmer sticking out from my tank. As far as the cost of the build, On his site it listed the parts cost (with a cheap pump) around $170. If one decided to use a much more efficient pump that they would have to purchase, that brings the total to about the same cost or more than One of the NW200's with the pump modification (Sicce psk2500). I'm sure you have seen the trends lately with skimmers. A tall slender skimmer is no more efficient than a short wide skimmer with a bubble plate. IME, most DIY stuff that we try to do, end in costing more in terms of time and energy and redesigns than they would have cost just to purchase a decent piece of equipment in the first place.
As far as the Mag pumps are concerned. I think you don't hear as much about them being used/modified because there are better pumps out there. Most people tend to stick with pumps that are already proven as good skimmer pumps liek the Eheims, or choose to go the cheap route (which is what most DIYers are trying to do) and use a much less expensive but more powerful pump. If it were me, I would spend the inital cost and just buy one and see if it fits... if it doesn't then send it back...instead of spending all the energy trying to find out (along with the hassles and headaches) if it will work....but that's just me being silly I guess.