I would really like to see:
- Guild ladder for different formats
- A /fame or /rank command like in GW1
- 2v2 or 3v3 in small arenas (gladiator style)
- 10vs10 “Kill the Lord” with short respawn time on large maps with strategic points (portals, flag, catapults, guildlord) -> classical gvg
- 5vs5 MOBA would work REALLY great! Starting with a LvL 80 character with white equipment, no traits and only one skill. Killing enemies grants money which is used to buy skill-scrolls and trait-point-scrolls (for unlocking). Also you can buy better equipment and upgrade units. Just an idea.
- 8vs8 return of the old Hall of Heroes (system). Kill count, king of the hill, capture the flag/relique run and of course deathmatch.
All this can be done in GW2. Just use your imagination :D