EXP would be nice but i don't know if that something you can change in the core game
Because Bungie would never have changed anything, and would have just kept everything the same? Yet every Halo they did, had things that changed. I also play Destiny, and have noticed that many of the things people claim Bungie would have never done to Halo, they have done in Destiny. You may not like the direction 343 has taken, but that doesn't mean you would have like the direction Bungie would have taken.
Halo 3 had the best ranking system and we nee it back in h6. I think its ok to be able to get to general with just exp because 1. It took A LOT of exp to get there if just using exp and 2. You can always see HOW they got general. This way, people aren't feeling left out and everyone has a reason to play. Plus, if you win a game, you learned something, so it makes sense to get exp. The only other thing I want in the h6 ranking system is that you can gain exp or something if you carry the team and still lose. Make it more personal. Not just win or loss. This would show a truer representation of their skill. This happens a little in h5 but the opposite way where as you cant rank up as fast if you get carried.