DayZ is not "built from the ground up"...
It's the ArmA Mod... running on the ArmA 2 technology except in a stand alone application independent of the native ArmA 2 content.
I can't imagine that it's all that different from the mod itself in terms of functionality and overall impression. It'll have some more polish, more tweaks and customization to the overall interface, but that's it. Same game, same challenges, same problems.
Same potential.
Now if it was properly adapted to the ArmA 3 technology... which it should have been, but that would have required a lot more "built from the ground up" in terms of having scratch build and adapt proper content, and not simply port resources for the core game. There was lot of media resources that were simply retasked from the native ArmA 2 resources, from the map of Charnarus to player and object models.
That is probably why it isn't on the ArmA 3 engine like it should be and deserves to be.