The biggest reason I wouldn't want a paracord belt is that I don't really like the idea of cannibalizing my belt; I am wearing one for a reason! I'd rather plan on having some spare cordage that won't compromise my clothing system and my ability to carry gear on my person (like my belt knife).
At first blush it looked like this design addressed this weakness, but it looks like the paracord is still an integral part of this design and that using the cord would render the belt useless.
In my mind, for what its worth, it seems like a better design would have the belt be a single piece of leather instead of having that couple inch gap in the middle (as seen at the top of the following photo). This would allow you to use all the cord and still have a working belt.