I guess my first question would be "Why bother?" Granite would need to be attached to something else to be adjustable, unless dovetails were cut right into it, and I think that would make the cost extremely high. Unless. of course, it is being done in China where labor is still relatively cheap. I think jointer quality is mostly dependent on the cutter head and the ease of adjustability of the infeed and outfeed tables. Are the planes parallel and can they be adjusted over time if need be? it is easy to get the outfeed adjusted to the cutter head, etc.? Cast iron is pretty stable and it may be dented but it isn't likely to chip.