Easiest thing to do there is use the "campaign" heroes, you can build unlimited of them if you allow them to be trainable at an alter or barracks. (you can do that with the normal heroes, too, I just don't remeber how to do it off the top of my head.) And simply remove the "revives dead heroes" ability off the Alters/Taverns. (might be a true/fals box you have to check)
-VGsatomi