For the main menu, I'd use the main menu theme from Tiberian Sun.
For load game/skirmish menu, and battle selection map, I'd use a mix of the general map theme from Tiberian Sun, and the GDI and NOD map themes from Tiberian Dawn.
For the mission complete summary, I'd use the "Great Shot" theme used in Tiberian Dawn.
I don't know if it's workable. Or, if it's too much work or could cause bugs or problems, don't worry about it, just thought I'd put it out there. It would be awesome to hear the Tiberian Sun map theme in the background as NOD or GDI brief you on your next mission.
