You already have TDM, its called battle. TDM is the LOWeST evolutionary form of multiplayer, you shouldnt be asking for MORE of it.
You should be asking for more sophisticated objective play like TF2 PAYLOAD (moving objective), QWTF Hunted (protect the VIP) or FPRTSS (first person real time strategy shooter) like Natural Selection & Empires mod for Halflife.
Or even better, combining ALL OF THESE.
A moving carriage with a VIP. Each team has commanders to issue orders and setup the defense/ambush and does not participate in the battle. Instead sees a different view (2d or isometric) as the battle unfolds.