A Little Ancient Mesopotamian Campaign Setting With Your D&D, Sir?

Inspired by this approach to hex mapping and setting design, and at a bit of a loose end (you know how sometimes when you have a million other things to do, you just can't help doing something else?), I today drew up this beginning campaign setting map:

The regional hexes are 5 miles; the subhexes are 1 mile. My approach was basically similar to that of The Welsh Piper, but slightly looser and more simplistic, and can be summarised as follows:

• Choose three terrain types: primary, secondary, and tertiary. In this case, scrub hills, evergreen hills, and grassland. The climate is semi-tropical and somewhat arid; for the evergreen hills think cypress trees in the Levant rather than Norwegian firs. 
• Make the centre subhex the primary terrain type. Then assign 9 primary, 6 secondary and 3 tertiary terrain types to the 18 whole subhexes, and distribute to taste for the 12 half subhexes. 
• Roll to determine the primary terrain type for neighbouring regional hexes, based on the terrain types for this regional hex (roll a d12 to determine: 1-6 is primary, 7-9 is secondary, 10-11 is tertiary, 12 is a wildcard.
• Draw rivers, lakes etc. as desired.
• Place a settlement, a dungeon, a resource for the settlement, and three 'known' miscellaneous potential adventure locations. This are all the places the PCs are aware of at the start of play. 
• Fill in information for all the other hexes; but that information is secret.
• Profit. 

And you don't do anything more than that except for broad strokes. So here are the broad strokes:

• It's an ancient Mesopotamian, early bronze-age type society. It is not remotely accurate to the real world geographically, culturally, or historically. It's to ancient Mesopotamia what D&D is to medieval Europe. 
• The players start in the small walled town of Eshnunna, an independent state of a few thousand souls with a wall around it. The inhabitants mine tin from the hills a mile or so to the North, and graze sheep and goats on the shrubland hills nearby. The grassland to the East is part of the range of a nomadic tribe of herders who are there sometimes depending on the year and the climate. They have a frictive relationship with the people of Eshnunna.
• The hills surrounding Eshnunna are home to monoliths and monuments of an older civilization which they refer to as 'Sumer' and which left the area a few generations ago. This older civilization practised magic. Mastering the language of Sumer and deciphering clay tablets containing their spells makes you a magician.  
• However, there is a more ancient and half-buried ruin, called Jemdet Nasr, which is home to something altogether more frightening which the locals largely shun. It was inhabited by a people who are referred to as the 'Ubaid', who disappeared thousands of years ago, and who worshipped what are called the "Other Gods" or "Satan" ('the Adversaries') by the men of Eshnunna. These Other Gods are said to lie sleeping beyond space and time and are more powerful and terrible than the Gods of Earth who the men of Eshnunna worship.
• Jemdet Nasr is a Mythic Underworld.

And as a bonus, two alternative rules for bronze weapons:

Lazy variant: On a natural 20 the attack is 'critical' as normal but the weapon breaks.

Complicated resource-management variant: Each bronze weapon has a twenty-round 'life'. Every round of actual physical combat the weapon is used in, chalk up another notch. When the tally reaches 20, the weapon has become blunted and useless.