From my long experience in both MMA and BJJ focus on increasing his maximal strength and explosiveness in the weight room. His endurance training will mostly be taken care of in his actual sparring sessions, which can’t get any more “sport specific.” Focus on big multi joint athletic lifts for pure strength and explosions. Think squats and push presses. Combat athlete are like any other typical power athlete, they just need to move more efficiently(more mobile/stable) and become more powerful. Just improve his overall athleticism. You won’t believe how much most combat athletes can improve with a simple program like that.