All of the following is in MY OPINION however if you agree or disagree with anything please say, or have suggestions of your own.
Multiple gamemode playlists: like big team battle and rumble pit, this will condense the playlists so 343 have more space to add extra playlists that the community are asking for. BTB could contain Dominion, slayer, CTF and another
RP could contain regicide, slayer, slayer pro, KOTH and oddball. Slayer playlists would still be present but objective gamemodes could be removed apart from the most popular ones. This would leave space for 2.
A competitive playlist for hardcore gamers and a community playlist for forge creations. I myself am not a competitive player but many are complaining that they are being dumped with rubbish players, there is no skill ranking system ect. If they were given there own playlist the problem would be solved. Also important is the community section. This gives more reason for people to forge and gives more diversity to the multiplayer. modes like slayer, flood and race could be suggestions.
So: As 343 wants 10 playlists it could look something like this: 1. infinity slayer 2. Big team infinity slayer 3. Rumble pit 4. Big team battle 5. flood 6. MLG or something 7. community 8. DLC 9. swat and 10. can be a trial spot for new modes (eg. multiteam, team snipers, team regicide, griffball ect.)
Grenades: grenades are not as powerful as they were before, even with the perk. I understand you might not want to make them do more damage as it might have been done on purpose but please take out grenade indicators. Even if a grenade was well aimed a player can easily avoid it. They are unnecessary and altered the principal halo has always worked on: Grenade, weapon, melee except now the grenade part is almost gone due to them being not useless but not as useful as they should be.
Balancing: Whilst 343 have done a pretty good job in balancing weapons there are a few that need sorting mainly the DMR being overpowered and the carbine being underpowered. The DMR is just the best precision weapon out of all of them due to its large zoom (especially on big team slayer) its large clip and its powerful damage. To nerf it 1 of these 3 areas need to be addressed. It just means that the other 3 precision weapons are practically pointless when the DMR is superior in almost all situations. The carbine is weaker than the magnum so that needs to be boosted. The bolt shot is debatable at being overpowered. If just the DMR was sorted matchmaking would be much more interesting as players would have a variety of different primary weapons.
There are other small nitpicks I have but they don’t detract that much from the over all experience. I very much enjoy halo 4 war games but these changes could keep me hooked on it until halo 5.