The appropriate use of this technology would be to make rendering dirt cheap and then apply style transfer as a constant overhead. But really, it should be something the game does. Like if you develop on some 500 FPS relic of an engine, but train with offline renders of whatever you want it to look like. Full global illumination, true subsurface scattering, flawless hair sims. all that fancy shit. Spend an hour path-tracing each frame. That's the look you'll fake on top of a fullbright Source g-buffer.