Of course i can flee from battle and left the caravan and acting like I am free to choose fight for them or not, did not think of it in the encounter. There is another problem with fixed tie to the caravan: we cannot enter settlements to buy something, especially food. So if we mistook with adequate food amount signing contract, we can loose men deserting us on the route.
And i did not ask this, is that orc marauders band was just a part of the world environment, or it was generated to attack caravan when i took the job? Was it a coinsedence or a mission concept?