That actually would have been awesome to play. Think about the situation: You're completely surrounded by the enemy, all alone, there may be no help coming for you whatsoever, and you've got to fight your way out and find a way home.
Of course, one reason they may have cancelled it as well was something that happened in the novels. The person who trained Delta Squad personally went to Kashyyyk looking for Sev, but found no trace of him anywhere.
I honestly feel like this should be based around a RC Team, an elite, 4-person squad sent in to make sure the army can get in. Reminds me of the final mission in Republic Commando (RIP RC-1207 Sev).