For example, on Halo 3, there are several playlists for map packs, the best by far being Team Mythic. Why is not in Halo: Reach!? Sure, there’s the Anniversary and Premium playlists, but that’s it. And they are virtually dead. Why not add more playlits just for DLC? This would rake in some more cash for 343/ microsoft and would make people like me very happy 
Also, the damn achievements would be possible to make… well done on that, by the way.
For example…
.Big Team Defiant: 8 v 8 Slayer and Objective games on NOBLE/ Defiant maps.
.Race-iversary: Race game modes on Anniversary maps. (8 players)
.Premium Firefight: Firefight games on Unearthed and Instillation 04. (4 players)
.Co-op Anniversary campaign. (4 players)
.Lone Wolves: Free for all game modes on all map pack maps. (Max part size 1. Players, 8.)
. Team objective: Same as Reach but for map pack maps. Possibly replace original Team Objective.
. Defiant slayer: Slayer gametypes on Defiant maps.
That’s just a few suggestions. What about you guys? Any ideas?