That'd be huge undertaking though.
Not to mention working with an engine and tools that they might not be familiar with, which would add extra time to development as they learn to use them.
At the same time, depending on the quality of the 3D world that you suggest, would make plenty of users unable to play the game at all, due to hardware requirements.
What I said about VNs on Unreal Engine, I was meaning your standard prerendered 2D art and world, just like as if it was in Ren'Py. Basically a pointless waste of something like Unreal Engine's capabilities.
Funny, you say you're not saying that but I swear I can see you saying it at least twice...