All talk about making The Headmaster switch to DAZ seems like a hypothetical question. Reality is that if that happened, all the images would have to be remade from scratch and quite possibly all assets used in the images too. While it may have visual improvements, reality is that the workload is unrealistic. I posted ages ago that this is a discussion for the first year of development and after that you would just have to hope you made the right decision because you are stuck with it.
It's kind of like the posts, which happens from time to time where people argue that it should be a real time rendered game because that way a scene can be made once and clothes can then be switched by the player real time. Ren'Py can't handle such real time rendering and rewriting the entire script for a brand new engine at this point seems like a whole lot of work too. Writing some game for the Unreal or Unity engine, which can take Ren'Py scripts would be awesome, but it would also be a task, which would take ages even if people know what they are doing.