I don't think we've seen any indication that the Federation has the technology to perform planetary engineering on such a scale. It's also an illogical extravagance given that they can just use spaceships to mine ice from the system's cometary cloud. And why keep the ice in orbit? Why not just send some comets to disintegrate in the atmosphere and add more water to the planet's own supply?
Besides, given that one of the components of the 40 Eridani system is a white dwarf, i.e. the remnant of a star that swelled to red giant size, it's likely that the inner system has been stripped pretty much bare of water and other volatiles, which may be why Vulcan is so arid. Any such icy world would have to have been brought from pretty far away, at least the Oort Cloud. It would be a monumental effort.
And of course it's an unnecessary postulate. Occam's Razor says that what we saw was an illusion within the mind meld. That's by far the simplest explanation.
Besides, given that one of the components of the 40 Eridani system is a white dwarf, i.e. the remnant of a star that swelled to red giant size, it's likely that the inner system has been stripped pretty much bare of water and other volatiles, which may be why Vulcan is so arid. Any such icy world would have to have been brought from pretty far away, at least the Oort Cloud. It would be a monumental effort.
And of course it's an unnecessary postulate. Occam's Razor says that what we saw was an illusion within the mind meld. That's by far the simplest explanation.