Live2d's has 2 differences I can see.I am going to admit I am not the most adept graphics pipeline guru. well lets go novice. I understand some of the concepts but never in the line to practice them and it was never anything I was interested in fully exploring, so take my understanding from that point of view.
My understanding of the current graphics pipeline is that it is tied to some propriety assets and possible tools that Vren cannot easily release the assets to public open source. Adding Live2d starts a process that gives some wiggle room to allow mods more freedom from that aspect, It also greatly reduces the complexity of certain aspects of the render system, so it may be possible to add jewelry, tatoo's etc., finger nail polish was even talked as a possibility.
that said, some of the things shown in the tech demo require animation so I see this as a first step.
but the live2d stuff is suppose to be more open to modders
the first is it allows more control over proportions of the model. Second it allows making modifications to clothing templates some what easier in that you can add patterns to them. That said not to sure how useful that will be.
If you add a pattern to a dress of character standing it will not transfer the same way to the characters 2D image if she is in another position.
Vren is using daz3d if I am correct. He probably doesn't own the full rights to the models. Which means he can't simply release them to be used by the modding community. If he had made his own models then he could.
Frankly with all the work he is putting into the live2D I'd say he would be better off if he made his own models, dropped renpy and went full 3D. He could still use python and do it. It would require a bit more work in the long run but would be worth it. It would really open this game up for modding then.