I've been cheating on that one a little bit, myself. Tabletop Simulator gives me most of the tools that I need to do tabletop wargaming.

What it doesn't do is make my life easy when it comes to importing my own assets. Tokens and chits are really easy, don't get me wrong. Models, on the other hand – it utterly objects to fairly standard object models with image textures which have no good reason to fail. Their documented workflow goes through Unity, which I have absolutely no use for it all.

Emulate some of that environment with the flexibility of easy asset integration, and may be a somewhat better scripting language to connect objects up with and you very well may have a killer app.