I have now given up on my previous 'cube in a hole' megaproject (
http://www.mkv25.net/dfma/map-3555-yellowbanners) and I am now working on a new, completely above ground lake castle. There will be no underground mining what-so-ever. To obtain stone, my only digging will be on the surface to landscape the large artificial lake. After all the lake digging is finished, my dwarves can remove all of the stone in the lake (for building purposes) and then channel water into it from a brook or a stream.
At the moment I'm looking for a spot to start work on, I need a 3x3 area with a small corner of a brook, no aquifer, a soil layer and then a limestone layer and it has to be completely flat. It should be pretty easy for me to find so I am not to worried about that, I am more worried about how bad this project is going to be on my FPS.
Edit] I have drawn out a plan that I might aswell post here:
1) Smaller islands - Just an aesthetic thing I thought might look nice.
2)Gatehouse - The gate house will be out on an island with its only access being a bridge from the castle and a bridge from the mainland. I will also have a third bridge that will give my dwarves access to the two towers from within the safety of the castle
3)Keep - The keep will be were most of my dwarves work, sleep and eat.
4)Courtyard - The courtyard will contain a barracks, a farming area, food workshops, trading area and a butchery/tannery/leatherworks building.
5) I only want a small bit of brook on the map as it is all i need. This brook corner will fuel my lake with water after its excavation and clearance has taken place.
6) A road will lead all the way into my keep from the outer edges of the map.