I'd rather add this feature to recastdemo; after all, it can read mmaps fine, so why not make it read a custom pathing info format, or even sniffs for that matter. Could invoke WPP, only parsing useful packets, and make it dump data to a specific format in a target file that you then read from. That would take care of any build.
"Fixing the grid system" is awfully vague. It doesn't tell to what extend it is broken. And in fact, it's not; there's just limitations that are not easy to ease / remove (see Dalaran visitors). It works fine; all it needs is comments, but go tell that to whoever designed it, because that person has long since vanished.
As much as I love 4.3.4, i hate to see Trinity stagnate, and think that going back to being on retail's patch will bring back interest and motivation.