Yes, music is the next step. That would fill the remaining 3.1 channels, because the fight itself is only stereo. Ideally it would be composed by John Williams, but I suppose any other Star Wars source could potentially work.

I’d also need to figure out how to sound mix the parts of Kylo outside of the vision. Stuff like this is something I’m completely inexperienced in, so with Hal’s commitment to assist with this project I’m probably gonna have to rely on that. But I’m not going to officially request such a thing until the dyad duel and hangar scene are taken care of, which is ongoing thanks to him.

In other words, we have a long road ahead of us, but that’s fine by me. It gives us more time to brainstorm our options. Especially in the case I overlooked something.

EDIT: The two that stand out to me in terms of the saga itself are the following -

A Jedi’s Fury - starts out very subtle and creepy, and suddenly is very intense. You also have the Emperor’s theme here, who Kylo is technically fighting in this scene, anways. Granted, this may be way too grandiose for a scene this early in the movie.
The Duel (ESB) - pretty self-explanatory