The only way I could see it working was if it was done in Galaxies, with a pricing structure that lowers the cost for an additional galaxy, provided you get a digital copy (It'd be too hard to do a hard copy for less based on owning another galaxy, without buying them in groups, which is possible (Say, the cluster of galaxies around the Eye of Terror) but would still take an awful lot of planning and other fun stuff). At least that way you can pick and chose the galaxies you want, reducing the space consumed on the HDD. It'd have to be done based on the growth of the community, though. There's no point having several dozen galaxies with only a few players per galaxy, as I'm sure you're aware.