I believe they should fix these following issues on Halo: MCC.
Get rid of "Halo 3" Game-mode, replace with "Halo 3 & 4 Grifball" The Sport that started it all.
Get rid of "Halo 2 Anniversary Rumble" and replace with "Team Snipers"
Add Halo 4 to Team Slayer
Fix "Connecting Server" issue when players found and not able to connect to host.
Find reliable host to connect to (Like above issue) before launching client.
Nerf the Battle Rifle for gods sake (Halo 2 Anniversary)
Fix the damage on the Halo 3 Battle Rifle (Up it)
Add more preferences to Halo 3 & 4. I didn't just buy the game so I could play Halo 2.
Branch out game types, instead of "Halo 3" (The most awkward reason to add that in... we'll never know) And make it so you can chose "Halo: CE / Halo 2 / Halo 3 / Halo 4" games with a variety of game types for said game.
Make dedicated servers in the East & West of North America... please (If you don't already)
I think that should please me. What about you? Discuss.
If this happens, i'll dance like Duane.