I was listening to a song from Kingdom Hearts (Forze de male, in case you wanted to know) and noticed that the notes at 1:30--1:40 sounded like the opening notes to Halo. Things just snowballed from there...

We all know that Halo was meant to be an RTS, but what if Halo was an RPG?
--The game would start with the Fall of Reach.
--The campaign mode would be called "story mode" and would be twice as long and in-depth.
--MJOLNIR armor provides +5/5 defense bonus.
--The story would be riddled with flashbacks to Master Chief's childhood and military career.
--The music would be written by Nobuo Uematsu.
--You know the fanbase surrounding Sephiroth? Transfer that to Master Chief or the Arbiter.
--Halo 2 cliffhanger ending? Nope.
--Miranda Keyes would get killed by Tartarus, then your entire party (Arbiter and Sgt. Johnson) would fight him for dominance over the Control Room
--You'd spend hours in the Library "leveling up" for the big boss battle at the end.
--Annoying random encounters.
--The boss battles against Regret and Tartarus would be much better.
--Goodbye Bungie Studios, Hello Square Enix!
--Master Chief and Cortana cosplayers would become VERY frequent at conventions
--MJOLNER armor would resemble a small Gundam.
--One of the bosses in Halo 3 would be Gravemind, and you would fight him a la Oogie Boogie's house in Kingdom Hearts (running around the area fighting Flood infection forms while trying to destroy certain parts of his body to kill him).
--Truth would steal Sephiroth's position as most evil video game enemy in video game history (well, maybe not).