Mcmjon brings up a good point here, which is that the team defending the flag will always have an advantage because they can all port to the flag as long as they control it, regardless of where they are. The offensive team either needs to walk there in force, which means they are losing coverage elsewhere, or they need to risk the dreaded flag gank, which is becoming more mainstream as we gain experience.
This really comes back to the question of momentum. If my team has control of all the flags we will probably keep them, as long as we respond to cap attempts quickly and in force. Relatively complex strategies like feinting one flag but going for another while your enemy waits on their ports to cool down are viable, but only at really high levels of play. As flags rise in importance in later builds you will see this issue becoming more important, but it comes back to one thing: Is momentum something the devs want to encourage or discourage?
Also, really nice diagram, mcmjon. I hear you race motorcycles?