I think that you might be able too because i think i heard from some magazine that they still had a secret game mode that would kinda be like online co-op thingy with objectives and one team would be covies and the other Spartans. they also siad there would be a coive that could climb on walls. I have no idea if this info is correct so don't take it too seriously
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Im not sure how fun it would be, it wouldnt be like halo anymore it would be wierd. I'm actually really not sure how it would play out either.