Here is a list of the things I wish They would add to Halo 4 from all of the previous Halo's.
Halo 1 (I was late on halo 1 I came around right before Halo 2 came out)
Campaign. Halo 1 was my favorite campaign for some reason.
Halo 2. (My favorite game of the halo series.)
Button Glitches
Super Jumps
Butterfly Glitch
The ability to get out of maps and roam around.
Juggernaut Gametype Hide N seek + gametypes like Demolition or Cat and Mouse on Coagulation. (I loved being able to ram the warthogs into each other and blow them up)
The Symbol ranks for the last few ranks (EX. Level 50 was a Halo Ring)
Halo 3
Graphics/ map builds (I liked the graphics better than Reach and the maps mostly had a really good feel to them.)
Theater. (Never really used Reach's)
Zombie Gametypes.
Ranking System
Matchmaking playlists. Plus bring back The 1v1 playlist. The stuff like V-Day Massacre they added.
Halo Reach
Forge Mode.
I didn't add much from here because I just don't like the feel of reach. It didn't feel much like a halo to me because of how different the movements and shooting is.
Miscellaneous
Direct Upload from theater to computer. or a website to pic the videos up from. (Kind of how COD Elite is set up)
Something Rare for people to work towards. Ex. Certain secret achievements for something like the recon armor.
The gameplay from H2 and H3. Like jumping and shooting and just movement. It just felt better than Reach.