I can't speak for the server side of things, but for general playability i'd like:
- Destructible or modifiable terrain so you can destroy buildings to direct line of approaches and create cover.
- Better character movement. I need to be able to climb, crawl, shuffle, peek, blind fire etc.
- Guild challenge / Epic battle. A large scale guild battle that filters down through maps so that only the best go through to progressively smaller maps. 100 vs 100 down to 10 vs 10. or 1 vs 1 with 198 spectators (or more).
- photo realistic faces. I want to be able to paste my ugly mug on the characters face and have his lips move when i speak.
- a points system that rewards squad level interaction higher than one man band gaming.
Visualize: A large scale map supporting a massive battle. Squads are players grouped together according to ranks/points earned, with a dedicated chat channel. Only the squad leader communicates with the overall leader. Dutys are passed down if you are killed, so if the commander gets killed, he will respawn, but the duties have passed to the next man down. A 'tactics' rank would score you on how well you set up the men under your command and how well they performed, so sending noob squads to assault a fortified building would be bad, whereas using experienced players to out flank and pinpoint some mortar fire before a combined assault would rank you higher. Combined with fluid mission objectives ranked as for and against from player level to guild level, so over a course of a mission objectives change from attack this spot to defened against this attack to counter attack and capture building x. Add in the flavours of cod modern or battlefield or AA with a usuable map editior and extensibility , then you would be onto a winner.