Two major things I'd like to see in Halo 4 would be:
1.) Return of Clans: When I first started playing Halo 2 this feature of setting of a clan was under advertised but well utilized by myself and others online. I think it was one of the key differentiators from other games at the time and since then. In the fledling world of console online gaming it provided a real opportunity to identify with others once joining and enabled a sense of community. Since its removal (and other changes) you still see people wanting to identify with a group but not having an ingame means of doing so. As the leader of my group (clan) I can say with absolute certainty it was one of the main reasons my group stayed together through the years playing the halo franchise as well as others. Of course as games, online gaming, and gamers evolve so to should the concept of a clan and its offerings. I do not expect 343 to provide a medium where by a clan could tie in accomplishments from other games or consoles. I'm merely asking for the ability for clan matches, clan rankings based on those matches, Clan messaging, ranks (modifable to a standard more like WoW vs the original fewer levels of Halo2), and of course clan medals/achievements.
2.) Disable Xbox Live Party Chat while in game/combat. Once we saw the evolution of Xbox Live and its dashboard go from the afterthought (and background) of our consoles to the forefront of our experience we started to lose the very thing that brought us to online gaming, the interaction. Currently when you play Reach or any other online multiplayer game you can join a team of people that potentially could all be in completely separate conversations through their own private party chats. In my opinion this is counter productive to not just the game but the online gaming experience. We don't see our beloved NFL players on each play with a cell phone in their ear and calling someone else while trying to score. No, we see everyone get on the field and play each play while communicating with the players that are 'in play'. Once off the field (out of the match) you should give them the option to go back to their previously established private chat. This change in both xbox live, hopefully lead by this release of Halo 4 would redefine our online gaming experience. It would encourage people to actually plug in their mics and open their mouths to communicate with their team mates. All too often (log in and experience this for yourself sometime) you will start a Halo matchmaking game and maybe 2 people out of 8 have mics plugged in. When you DO get more than 25% of the players to plug in their mics they are in those private chats with other people. Can you imagine trying to capture a flag, defend from an assault, or just communicate in battle without the ability to do so? Why do I think this is a Halo 4 issue and not XBL in general is because the Halo franchise helped birth Xbox Live. It wasn't Rainbox Six, or ChromeHounds, or CoD, it was the Halo franchise that set the presedence for how we as gamers wanted to interact with each other. Its how people enjoyed their downtime by connecting to their friends through their consoles vs their PCs and making bonds despite geographical distances. If Halo 4 would be the first to have an intelligent party chat disable option you will see this applied to other games and have a ripple affect across all of gaming.
Please consider both of these suggestions as I think they would really add value to the franchise and gaming in general.
Thanks for your time
-DCScorpio