Its nice to see that he seems to has a strong interest for Sikhi. I just think hes misguided. Perhaps he could take amrit, live a practical life and on the side teach Martial Arts to the Sikh youth
Would it be ok for him to fight without wearing his Karpan/Kara? I'm not sure if he is Amritdhari or not but can see this being an obstacle. In fact for an Amritdhari this may be an issue in many sports...ie other close contact sports, swimming etc. Covering his hair should not be a problem as long as he can wear something that will not come off in a headlock or when grappling.