I think perhaps increasing levels of FF to match with the difficulty would be a reasonable idea, and perhaps the money leech system works aswell, with an easily accesible setting for the serer.
For greifers and trollers, I noticed no-one has brought up the vote-kick command.
I think it would add realism to the game, as these situations (I have done these I admit) occur:
A) person A is swarmed with clots and nearing dead. Person B sees this and chucks to grenades at A's feet. A lives, all clots dead.
B) everyone (except the demo) stand on a huge pile of the demo's pipes on the final round, waiting for the pat to (hopeuflly) come up and maul them, only to trip the mines.