I haven't had a chance to play a RZ yet, but I'm number 292. My opinion here is less than useless given that I haven't played it, but from watching streams it almost feels like living dead girl can slow you down from making progress in the game. Good points, I love the easy add a ball on a tough game, but you can't lock for house of a thousand corpses and it doesn't work with modes. It would be nice if there was another objective in the game to qualify for wizard mode, something that you could progress while in living dead girl, something like the killer cards, but it reaches deeper. Am I out to lunch?
Edit: I was thinking a bit about what the long term objective could be and a few things jumped out. First and foremost, loops seem like an obvious thing that could lead to something in the game. Many many pins have had loop rewards and counted your loops, but given the flow that this table has I think it would be really satisfying to get to something for 100 loops or whatever or to introduce a combo strategy. Could there be a 3-4 way combo that exploited the ramp? Could there be a combo that drops the house of 1000 corpses drop target for the last shot? Just some ideas.
Second would be like a robot boss battle or something based on pop hits. You rack up a lot of pops going to for living dead girl, this could be a nice thing to make you feel progression after bringing her back to life.