Sorry for the double comment, but to follow up my last post: How about a "Transform" spell or something. Like you pay 200/200 and you can transform orc/ice/undead spaces to one of the others?
Like its predecessor its a really great game. What it lacks is diversity in the later levels. After some point, you got all spots filled with, well, the only choice for the spot. And your rating is based on mere luck. If that one creep gets through or you cant click that scroll you want because there are 23423452 items on top, your screwed.