I think it would be interesting if players had the option to increase a Unity NM's level for more prizes, similar to Incursion and High-Tier Mission Battlefields. This would gives more experienced players a greater challenge, while not barring less experienced players from the same content and rewards.

I would definitely love it if there was something we could do with unwanted unity gear too, like either exchanging for Accolades, NM materials, or maybe even desynthesis. Urat's suggestion is pretty interesting too.