I believe 10k is required for Granny 3d. If a new map was made using Granny 3D, then it would have to be modded into the existing game (as you can't just drop in maps, per se). So, basically what you'd need is the money for the Granny 3d license, someone talented enough to design and implement new maps, and then minor modding support to get it into the game. Then, each player could download a "map pack" and then enable them via mod in game. Not sure if this would cause any problems over MP, but probably not.