I do not know if other campaigns "suffer" a bit the same problem as ours; But we often have a problem with adding actual role-play to the DW Campaign, as Marines don't really chit-chat much. And even when they talk to others it's often "Yes, Captain", "Out of the way, mortal" and most often "Die Xeno scum!".
So, for our last scenario I had my Marines start on a spiritual crusade as they entered their 20th year of marines in our Consecrator Chapter (we are running outside of DW), and then they were invited to a debate session with their Company Chaplain, who is of the more philsophical sort. I really had no idea how it would pan out, and if it would just end with "Burn the heretics!".
I used the Chaplain mainly to help answer detailing questions about the debate issues, so they could better understand the exact nature and help make their opinions.
Anyways, these were the 3 questions the 3 players and the Chaplain debated, and it turned out to last about an hour!
1) You have just successfully finished an engagement with the enemy, where you had allied with the Eldars to destroy a greater foe than was possible just with the marines present. The battle is now over, and the remianing Marines and some Eldar are left standing, victorious. What would you suggest be done with the Eldar, were the choice up to you?
[Questions that was then clarified further for the Marines: It was against Orks. It was to protect an Imperial World. We do not know why the Eldar chose to help. An agreement was made with them and a Chapter Captain. The Marines would outnumber the Eldars as it was right then and there]
[The replies varied from engaging the Eldars immediatedly, to giving them 5 minutes headstart, to honoring the agreement but no quarter would be spared if they met again - to forcing secrets of out of the Eldar before they could leave]
2) A Chapter Hero has lost his zeal for battle. He is still one of the most able and adept battle-brothers in the Chapter, but the fire in his eyes have dimmed. What would you advice him to do, or to be done with him?
[Clarifications: He is a decorated war-hero. He still completes all his engagements without fault. He has come to ask the Chaplains for advice, as it feels as if he is just going through all the same motions with all the same enemies on different planets that looks the same.]
[This one was one of the questions that took the longest time to debate. At first they could not at all understand how this could be - how could anyone not feel the constant burning hate for the God-Emperors enemies. Even with 200+ years of battles they found it hard to believe. The suggested asking if he would instead Train his brothers. They suggested that he should be send down amongst the mortals to see if he could try and remember what he was actually fighting to preserve. They suggested looking for greater challenges to him, than already]
3) A decorated Veteran Brother is feeling an increases lust for battle. He feels uneasy if he is not fighting, and all his time not in battle, is spend in the training chambers hacking battle-servitors to pieces. When fighting, he is always in the thick of battle and seems to burn with a lust for blood.
[Clarifications: This was meant to suggest a brother that was on the verge of feeling the call of Khorne, but without any actual proof of this, except an unnatural desire for battle, even amongst his brothers. The lust for battle is so all-consuming that it threatens to put his brothers at risk with the risks he takes. No signs of Chaos has been found in his mind or blood]
[Here they mainly tried to find a way to send him into glorious battle until he died. Or to somehow figure out if he was tainted, beyond what the chaplains had been able to establish]
Sorry that this became a bit more text than intended. But I hope others have a few good ideas I could steal for future Chaplain Debate Nights with my team