Here's a somewhat ambitious plan for a fortress I'm going to make.
First, I'm going to make humans playable.
I plan on building a giant above-ground city from carved stone. I'd like to use Sandstone, because I'm going for an ancient, Ur-like feel, where Bronze is the metal of choice and the city is guarded over by a giant ziggurat.
Every human will be organized into castes, and will recieve holdings in an approriate manner:
From top to bottom, Mayor, Administrators, Soldiers, Craftsmen, Farmers.
The Mayor and Admins will not fight, and will live in the ziggurat, along with the soldiers. The craftsmen will live inside the walls, and the farmers outside. Only farmers will havest, and admins/mayor will not haul. There will be no communal efforts: Greed and sloth are innate human traits, but common sense isn't.
The Stonemasons (considered craftsmen) will make the stone blocks, and the farmers will haul them into place. The farmers will not have stone blocks for their huts, only rough stone.
Durring a siege, all humans will be called inside. The farmers will be in the "Wall Guard", armed in Leather, Wood, and Bow/Arrows. The craftsmen will be "Gate Guards", armed in Leather and some Bronze with a Pike. The Professional Soldiers will be armed in full Bronze, with Bronze Spears and a Black Bronze shield (for epic-ness).
Each squad, militia or professional, will be of 5 men. The men will spend 2 months training, 1 month patroling/guarding, and the rest working. Professionals will spend 10 months training and 2 resting.
The wall surrounding the city will be 3 z-levels high and 3 tiles wide with 1 tile of fortifications in certain areas and walls in others. Ramps will connect the multiple levels. Stockpiles of extra arrows/quivers will be in small underground rooms beneath the walls.
The gate will not be protected by a giant drawbridge or a lava-moat, but giant, epic Black Bronze gates (floodgates) so that sieges may get in if they have building destroyers.
I plan on giving every human family their own hut/house, and when their children get married, they get their own hut as well.