Ok you might be right about this few things i kind of didn't think the payload mode through tho you are right needs big maps and lot's of understanding on how to make it.
Weapon customization and character customization a good thing for a game like this.It will make your game look more colorful and alive.
what about if you add vehicles and if a person makes a flat map of which you can fall off you may add a check box in the settings which will make invincible falls so you can't fall off.
What about a juggernaut level in which team is against another team both teams have a juggernaut which has lot's of weapons, health,Armour but moves slowly and both teams have to defend their juggernaut.for the capture the flag can you make it the team that gets up to 5 flags wins and not by the most kills.Finally you might want to make the jet pack look better than a black box.
I might sometimes loose of what i am thinking and write multiple comments instead of 1 so sorry hope it didn't get you too confused about what i am writing ;)