In a recent interview in Complex magazine, Cliff Bleszinski (Cliffy B), stated that he wanted to go as far as to get Master Chief into the final installment of the Gears of War franchise.
“I’ll let you in on a secret. I actually approached Microsoft on getting Master Chief into the game, but those guys are kind of squeamish. One of Halos successes is that its a soft M [rating]. Gears pushes it further. I’m creatively comfortable with that, though it can limit what you do. If you had to break it down, I’d say that Gears is like Mortal Kombat and Halo is like Street Fighter.”
“If we were to get Master Chief, we’d get his model, put him in a COG suit, make it blow up, and do some test animation work. We’d have to see what his head looks like being blown to smithereens or how his arm would look getting sawed off. Then we’d package up the test footage, put it on YouTube, and let the fans get a kick out of it because everything is meta these days.”
To be honest, if Master Chief was in the game, there would only be one game in the franchise because of the sheer awesomeness the Chief brings to the table and how quickly he would end it all for the enemy.