Since the hero creeps are permanent, I was hoping they'd be costed fairly expensive. I don't want them to them to be just other tactical tool we use and replace, at least not all the time. To be more precise, assuming power creeps are made out of "special parts" (maybe 200hp per part), my Idea is to make the maximum part limit open ended, but make the cost scale up exponentially by some factor. (I assume there's going to be a limit of maximum hero creeps per player at the same time, probably = to GCL?)
Lower tier players will be able to use typical cost heros, lose them and replace them. But for the top players, with an incredible amount of investments (millions of power), players will be able to make very strong heros(100 parts any one?). These units will be give those players a unique edge in conquering and defending rooms, but must be protected everywhere they go, because they are so expensive. The movements, position, and existance of such heros will be interesting to watch.