I know for a fact I'm looking at multiple Fortifications via multiple detachments, but then again I'm looking at a series of detachments to allow me all sorts of things, not the least of which will be my fallen GK detachment, small and cheap to provide me with access to a Flyer with Mindstrike Missiles. Welcome to the world of Auto-Perils! I think a castle list is quite possible, although until I reread the various Fortification rules in the new system I'll be somewhat cautious. 6th Edition Fortifications were entirely worthless except for the Aegis and Skyshield.