combine a number of branches with a number of glass to make a greenhouse. there would be no basement available and it would be one story.
options for benefits:
Controlled environment - Quality of seeds have no negative adjustment.
Layered growing spaces - essentialy it would be larger on the inside. able to grow more food inside than in the space the building takes up. no change to quality variables
Improved Environment - Plants grow in less time. no change to quality variables
Rooting Beds - ability to grow Plant based Curiosities. Herbalist Benches placed inside the greenhouse allow you to use a tree planter's pot to plant and grow new curiosities. quality of grown curiosities are alwasy q10. (yeah, you can mass-produce curiocities, but they will not be of the quality that you find in the wild.)
Secondary Ideas:
be able to place "Moat" tiles and to either build bridges on moat tiles OR use dirt to fill in the moat before being able to bash the wall. Moat bridges will not work over rivers.
Drawbridge gate units in addition to regular gates to cross the moats.
install "Wagon-Gates". simply an in-game modification to make it easier to do double gates.