Last tower I built was a mini-project (not near epic enough by board standards to be a megaproject). It was about 30-z levels high of marble blocks, half of which descended underground via an artificial hole carved into the earth. The bottom fourth or so I devoted to workshops and stockpiles, alternating between a work-floor and a stockpile floor with industries that had overlapping resource needs sandwiching their relevant stockpiles. The top floor here also had the drawbridge that led to both my mining shafts and the old fort 'ghetto' where I sent the excess migrants to toil. The bridge was designed to double-seal with both the bridge itself and a floodgate and a tiny brick stockpile was eternally resting near by to let me seal the entrance up in case of flying giant monsters.
Above these were the armory floors, two or so, that contained all the weapons, armor, and siege weapon ammo, followed by the barracks and training rooms. Right above these were the defense levels, with my best ballistas overlooking a front entry bridge and catapults for the other sides. The level right above that was carved up between a trade depot, finished good stockpile, surrounded by an outer ring of fortifications for marksdwarves.
Next came the office levels, carved up to give every noble a decent office, then the nobles quarters (most of these actually branched OUT of the tower onto big ledges. They looked pretty and were also rigged to fall off with the pull of a lever), and finally the sleeping quarters for regular dwarves.
The final four levels were, in turn, a food and drink stockpile, a massive dining room with metal floors (just steel blocks, the most expensive thing I had in great numbers) and artifact-storage area, an indoor farming level, and the top floor was an open-air outdoor farming level/game preserve/statue garden ringed with fortifications.
Everything floor was linked via a broad staircase that made getting between levels a breeze, but also proved my undoing when a flying Forgotten Beast in the caverns (that the tower-pit opened up into) drifted all the way up, got past the defense levels, and entered the top of the tower. Pretty much went floor to floor killing everyone. Only the slav... er, immigrant workers in the ghetto area survived and they were killed not long after via tantrum spiral that resulted from the lack of food, drink, decent living conditions, constant vermin swarms, ect...