They have bought into mangled maps and it would be a challenge to update everything for simple lat/lon. It would be easier to get every car in China to drive on the left, for them to change their railway gauge to 7' 1/4" or to move to the Swatch Internet Time standard. Think of all the title deeds, utility maps and everything that you need surveyors for.

As for military purpose, have you ever done any work with the military? Even though every army plays a good ballistics game, they tend not to be mathematicians. I would not want it to be tested, but my hunch is the mangled maps would work extremely well, even though their foes have had decades to do their own map making.