The Halo 3 map Guardian should be the newt remastered map. The flow of the game is great and the verticality of the map allows the players to be versatile and creative in how they play. I'd get rid of the equipment and replace them with similar armor abilities. The flare though should be replaced with the pulse grenades. The cloaking power up should be switched with damage boost or speed boost. Overshields should stay the same. The brute shot and Brute Spiker should be replaced with the Boltshot and the Suppressor. Everything else should be kept the same.
When playing on Guardian, you can shoot and kill the flying creatures that are around the map. In the remastered version, if you shout a flying creature, the rest of them should start attacking the players at random for a limited time.