My list: 
  
Gametypes: 
  
-Classic (no perks, no ordinance, no loadouts, no weapon indicatiors, 4 shot BR) 
-Team Snipers 
-Infection (not flood) 
-Team Doubles 
-MLG 
-Action Sack 
-Assault 
-One Flag CTF 
-Grifball 
  
Other: 
  
-1-50 Skill rank system shown in game 
-Better servers 
-More 4v4 maps ( DLC / Community forged maps) 
-DMR nerf / BR buff 
  
  
These things would complete the game for me.