Well, between the standard sprites, mack and the ds sprites (and those really only go with the ds tilesets) there is not much too choose from for most people for VX/Ace. At least as far as I know.
One of the reasons I wanted the rural farm set was that it had new sprites to go with it.
So, I think, a new sprite set, fully fleshed out, could offer a much needed variety in that area. There are already a lot of tilesets and portrait resources as packs available, but sprites? Not so much. If you are not a spriter yourself and you don't have the money to commission a whole new sprite set, then right now, you are a bit stuck with the standard rtp. This is why I think, there could be a market for sprite packs.
Any estimate when we can expect your sprite set?