I would guess you would need to unlock—I assume part of the reason 343 unlocked recon for everyone was because they wouldn't have the necessary or compatible infrastructure to interface with Bungie's systems. Beyond that I know nothing about 343's back-end systems so there's no way to tell what could or could not be done, or at what degree of difficulty.

I'm going to assume armor stays for the respective games, especially since Halo 3 and 4 aren't getting graphical updates and CEA never had special armor.