faster ways of expanding buildable territory

current landfilling way is really slow and need some alternatives:
adding buildable floating platforms we can build on (like oil rigs using),
platforms with concrete posts on the shore,
means of building vertically,
shallow coral reefs in the water, that we can landfill fast,
space stations,
additional islands,
underwater buildings (pipes, for example)
huge landfilling ships to speed up the process
some combination of stuff from above can help speed up the process significantly. cost of alternatives can be decently huge for maintaining game balance

Landfill paid with Unity perhaps?