Well, it wasn't my idea... but I like it. I made a mission like that, using FDF 1.3 and the townhall in Lipany one year ago. I tested it with my LAN-group a couple of times, but never finished it.
I have one suggestion, that is quite easy to do with very little scripting. Let the hostages be AI (it's quite boring to play a hostage anyway). Then the survival of the hostages can be the objective for both Resistance and East side.
Resistance objective is complete if the hostages are escorted to resistance safe zone. Consequently, East objective is failed at the same time.
East objective is done when the hostages are transported across the border, or where ever you think they should go to reach east safe zone. Then Resistance objective is failed.
This makes arather interesting conflict, because both sides must make sure that the AI are kept alive (and that is quite difficult when they run around in circles all the time, refuse to enter cars, get's lost, etc).
If the hostages are killed, both sides lose.