I've actually been thinking about having game modes other than the Renegade C&C mode. Here's a rough list:
Capture the Flag Mode: This mode is pretty self-explanatory. Each base will have a flag, and the team that captures their enemy's flag a set number of times will win.
Mobile Headquarters Mode: The Mobile Headquarters was a unit in Tiberian Dawn that appeared only for this mode. The team that destroys their enemy's Mobile Headquarters is the winner. The specifics would have to be different than they were in Tiberian Dawn, as both teams began with random vehicles and units, but I still think it could work with some tweaking.
Sole Survivor Mode: Sole Survivor was a game where players could pick any unit from Tiberian Dawn and run around the map collecting crates that will either heal them, or improve their firepower, speed, range, rate of fire, or armor. When the match time ran out, the player with the highest number of kills won. It's a little bit more luck than it is skill, but I think it would be fun.
Commander Mode: Each team will begin with a Mobile Construction Vehicle and the match will play out similarly to C&C mode with base building. Each team will elect a commander to oversee the construction of their base, but the commander can be voted out at any time and replaced. Build times would more than likely be shortened for most structures, and a team credit mechanic would be introduced in addition to the usual player credits. Team credits are what the commander will use to build structures and harvesters, and the team credits will increase with each harvester drop just as the player credits do. A cap would be placed on structures and harvesters, but other than that the bases would result from the choices of the commander.