i think that a green house would be a good addition to the game. it should cost 200 glass, 5 bars of any common metal, and 30 dirt. the dirt will be the dirt used for crops so i think that it should be what determines the soil quality of the crops. it should remain plowed forever preventing you from having to continue plowing and preventing you from digging it up to be used for other things. it should also have the same growth bonus as a beehive which does not stack with the beehive but you still get honey and wax if there is one in the green house(or you can add some wood and straw to have a built in beehive). the size should be about as big as a timber house or have multiple settings with different material requirements.
please let me know if this is a good idea and if not, why. :]