I think it's still a bit too early for multiplayer, and it might be a difficult feature to use.
To me modularity is the one part that falls behind in C2. I already talked about it, but making an RPG in C2 while having the possibility to make broad changes is still not easy.
For instance I'd like to use C2 layout to create all the location you have in an RPG, but being able to make broad modfications on all my layouts like Modifying layers disposition/properties/content mostly.
Things you can't really handle at runtime.
So yeah, I think modularity will go toward this idea.
Also modularity because a good game is seldom made alone. Being able to work with more than one developper would be a must.
And it would probably increase the quality and size of games.