Stupid question

Hello everyone, I’m aware of how silly this is and I feel as though I already know the answer but back in the day when bo2 came out I was young and sucked at the game so I never unlocked diamond (I didn’t even have gold on a single gun 😭) however me and my family play split screen very regularly to this day. Is there a way outside of unlocking them through online (which is practically impossible rn) that I can play with diamond on split screen? It would make the child in me extremely happy, thanks heaps guys glad to see there’s people still enjoying this game, my family have been playing together for around 10 years now!