Well there are two ways to get sequential ctf to work (prolly more)
I have a working system using the attack/defend mode (a setting on the intel entity)
The only down fall to this is, (unless it's changed now) that the flag carrier automatically gets a speed penalty. Back when I did mine, there was no way to adjust or remove it. Plus, the scoring for this game mode is broken.
The second way (look at avanti_b1 by sacrifist, a direct port of TFC avanti) is to enable/disable intel/capture areas (along with spawns) as the intels are capped. This way works better for TF2 (IMO) because the flag carrier does not receive the speed penalty. Also, scoring is not broken using this method.
I'm at work right now, but I would be glad to help you in more detail if you wish. I have a couple .vmfs I can upload as examples.
HOWEVER! I think CP will be more popular to be honest... the "give-gun-point-at-door" mentality of today's gamer is more likely to enjoy the CP style (again, my opinion). If it were up to me, I would release one of each! :cool1: that would be friggen awesome!