Yeah it could be cool... Hl2CTF's biggest problem is the lack of interest. 3 on 3 would be boring. I wish the game had more interest because I thought it was a lot of fun. Doing some 5 on 5would be fun.
As for right now, I'm not interested in doing CAL again. But as an abstract thought, it could be rewarding if the we just meshed with the game when it is released.