It just needs to play identically to Halo 2/3, with a gimmick like equipment so maps aren't totally -blam!-ed in the developmental process like with lolReacharound and Halol4. Reskin with next-gen graphics. Bring back the experience/skill system and the way that both tied together, expand the ranks. Oh, and COMPLETELY do away with all the CoD shit like custom classes and killcams (killcams are -blam!-ing useless in Halo and its combat style). New campaign, improved Forge, allow players to watch films in Theater together. Remake Guardian, The Pit, and Sandtrap. I still can't stress the ranking system enough. Also, in terms of graphics, fix the shitty lighting in the game. Not like Reach though where things looked pastey as -blam!-. Halo 3 had things great. Anyone else remember seeing Citadel map in the preview pics with the beautiful lighting coming through the roof? Yet it wasn't over-saturated like Halo 4. Basically a reskined, updated Halo 3. If you say "hurr not changing anything is dumb", you're full of shit. Halo 3 was #2 on the charts, years upon years after release, before lolReach took its place and fell to #3 three weeks after release. Halo 4 is now #8 less than a year after release, lol.

Good old arena style gameplay.

Revamped/remade Forge with new pieces and all the vehicles. (Civilian vehicles, air vehicles, space vehicles, etc.)