Thanks for the ideas, that's a lot of them

Are all of those player vs player -modes or are some of these supposed to be played with AI as well?
From a quick glance, to make the modes possible the game would need implementation at least for the following stuff:
Assault:
A1) max game time setting, with possibility to tell the winning faction by ownership of a specific base when the time runs out
A2) base setting which makes a base impossible to capture -- allows creating the spawn bases for Team B
A3) a boat or other vehicle which moves on water
A4) faction specific ticket settings, including unlimited
Capture the flag:
B1) The flag
B2) A few new animations -- is weapon usage somehow affected when carrying a flag?
B3) Triggers for announcements about flag capturing
B4) Marker logic / map view changes
B5) Monitoring for the flag to arrive at a designated area for a successful capture
B6) Score counting / max capture to end the game
B7) No base capturing
Intel grab:
C1) Should be pretty similar to capture the flag, except there's just one flag which spawns somewhere in the center
Demolition:
D1) Bomb item, carried as primary weapon by some? These guys can't shoot, right?
D2) A place where you can pickup the bomb
D3) A designated object or place where the bomb must be installed
Convoy:
E1) Probably needs a map with faction A owning travel start and end bases at start and faction B owns bases in the middle, with base capturing set off
E2) Somehow designate certain vehicles as targets, perhaps marking vehicle spawn points in the map editor, for the other faction to destroy to get a score, and for the owning faction to take to specific base / area
VIP rescue:
F1) VIP models, animations..
F2) Specific logic for scoring
F3) and so forth
Z1) possibility to define the used game rule set in the map or in content package
I'm going to stop thinking at this point for a while. Obviously each of these have quite much stuff to do, but none of the tasks seem specifically difficult to implement. If all of them are meant to be played with AI, then it might become a little more challenging to do. Most of the stuff the AI is able to do already should be usable in these modes as well, I guess the changes would mostly involve the AI commander behavior.
The game will evolve in modes department in the future, that's for sure, so it's good to see some suggestions thrown around already to get a better feel of what kind of stuff game modes should have an effect on.