Ball Pythons are not a social or even gregarious species, so they shouldn't be kept in the same tank, all sorts of problems can arise. But as to how big a snake tank can be, that really can depend on the snake IMO. But it's never good to use the full range of options a snake has in the wild as a yardstick for how captives should be cared for. A snake in the wild is an animal in a constant state of selection, and the pitfalls and dangers it will find are "meant" to either cull it, or allow it to dominate the gene pool for many generations. So if a snake as the whole wide grasslands of Ghana to tickle it's fancy, chances are it will opt for a precise microclimate that will be very close to what breeders use to hold balls in their racks.