Have a level (maybe the 4th level) of the campaign that has you travel into the heart of the city (make it a north american city and not just new mombasa) by warthog (or by a showcase of a new vehical). You will then fight your way to a skyscraper which you will then fight your way up in order to fight a giant creature the size of godzilla or something (could be covanant or prometian in origin) that you will fight with a hornet on top of the skyscraper
BRING BACK THE HALO 2 BOSS BATTLES!!!!!!!!!!!!!!!!!!!!
Also, add water combat to halo. There could be the unsc shark (a speedboat with a variaty of back mounted turrets) and the unsc whale, a giant aircraft carrier.
