There's no such thing as an OpenDingux build that is going to wipe out the original firmware. OpenDingux (or even legacy Dingux for that matter) can't be installed into the internal memory or flash ROM, so, even if it was possible to wipe the original firmware, you'd have nothing to gain from doing that.
With that said, there IS a boot loader available that will boot into (legacy or Open)Dingux by default, basically reversing the logic for boot selection, that is, doing nothing boots to Dingux, and holding SELECT on startup boots to the standard Dingoo firmware.
I'm too busy to find the link for you, but it's in here in one of the boards, use the search feature.