I would scrap the challenge system and put a whole new one in I would restrict all challenges to campaign so that the PvP players know how I feel. There will not be any of this kill enemy Spartans with UNSC weapons crap there would be none of this kill enemy Spartans with banished weapons crap there will be none of this kill enemy Spartans with pistol immediately after switching to it crap it be all just complete a certain number of multiplayer matches it’d be easy to unlock stuff in this game just like it is in the MCC