I GOT A PERFECT IDEA TO SATISFIED BOTH OLD SCHOOL HALO GAMERS & HALO GAMERS THAT LOVE THE NEW ABILITY'S!
You could make a multiplayer game mode (example Classic Team Slayer ) that takes of all the thruster ability's and new stuff etc. And keep it old school like the Halo 2 MP so all the old school players are happy. And then you keep all the other stuff for the other gamers that love all the new abilities. This way you keep everybody happy!