VN devs are probably gonna be your biggest market. Right now, the most robust tools we have are IllusionSoft games like HS2, Ai Shoujo, and Koikatsu. And of course DAZ. A new tool with maps made and submitted by the community, tools for making nonhuman characters and human characters alike, and maybe some animation packs for those of us who can't animate could go a long way towards this becoming a new standard. I understand about the licensing, though; that's definitely something to be factored in.
I think the easiest feature to implement is to allow rendered shots to have an alpha channel to automatically give them a transparent background. That way, VN creators can at least make sprites of the characters they've created. And, of course, a way to pose them.