That was kind of the original idea, although I reserve the right to mine out some soil to plant farms - mostly because I've already done exactly that. =P I thought it was later in the year, so I thought my food stocks were running lower than they are.
It is now mid-summer, and I have a bit of a castle built. It's roughly 35x35, located in the lower left of the map, and is the first of four I intend to build of this size. The upper left one will require more materials, due to there being a 1-Z level dip that would cut the castle in half otherwise. Once ready, each castle should be capable of housing a fair number of dwarves - I'm debating finishing construction of each, then dumping all remaining supplies from this initial trip under an atom smasher before abandoning the place and reclaiming with a smaller force. Divvying 56 dwarves up into four separate forts and seeing which survives the longest might be cool, if a lot of micromanagement. Maybe I'll make a fifth fort in the center to serve as the administration.
Edit: New idea! Each of the four forts only trains in one kind of weapon, with the central administration being full of nobles. Each fort is built out of a material that is the same colour as lords of the appropriate weapon type - something purple for the nobles, Cobaltite for the Axe Lords, Microcline for the Swordmasters, Cinnabar for the Mace Lords (if only because I don't know of a material that's the same colour as Hammer Lords), and Orthoclase for the Spearmasters. The cobaltite site is already ready to go, so it's a simple matter of atom smashing the excess, then reembarking with the appropriate materials to construct the other forts. What say the people?