One thing I've considered was embarking on flat terrain, and then digging down and carving out natural stone buildings. Basically dig down ~15 layers from the surface and make that your new surface layer. Leave huge pillars of natural stone that you carve into tall buildings. Farms on top of the buildings. Surrounding the whole thing would be a huge, thick constructed wall using all of that stone.
Its basically digging out a huge quarry and carving freestanding buildings from the quarry.
You will need a huge number of miners, masons, and engravers for all this and will likely need to turn off invasions while you're building at least the perimeter wall, and then once its all built you will have an obscene amount of stone that needs to be disposed of. SPEED:0 or adjusting the raws so that stone evaporates may be needed for this.
I'm waiting until the new release gets stable before doing this. Once all of the bugs are hammered out I plan on having farms and pastures on top of the buildings, and then city streets, alleyways, residential buildings, and all that other good stuff carved into stone.
For power just build a massive windmill farm on top of the walls. That will allow you to pump as much magma or water anywhere you want. You could even do a doomsday device that floods the pit the fortress is in.
I actually did start something like this way back in 40D, but lost interest in it when 31.XX was released.