This is again not a wishlist item, but something that was on my wishlist and Epic has begun fufilling it: Thank you for beginning to add support for SkyAtmosphere and ExponentialHeightFog to the path tracer (discovered this on github, less than 48 hours old I believe).
I had previously figured out a rather arduous workaround, where I used the MovieRenderCue to bake my path-traced scene, set it to pick up real-time fog in a separate pass, and then composited them in post. This will vastly simplify my workflow and allow me to stay in-engine to do my work. Thank you!