Basic idea

Make each play-through truly unique by randomizing the game world as much as possible at the beginning of each new game, with a minimum of new assets.

What to randomize

• Sector locations
• Sector selection (already partially supported)
• Starting locations
• City boundaries and sizes
• NPC locations
• NPC selection (i.e. spawn Ivan instead of Mike)
• Quest locations
• Quest selection (i.e. if new quests were created)
• Vehicle locations (Hummer, Skyrider, ice cream truck, etc.)
• Origin and destination of enemy reinforcements
• Others?

In addition, the maps themselves (i.e. placement of buildings, trees, ground tiles) could in theory be generated procedurally. However, hand-crafted maps are almost always of better quality, and creating routines that produce acceptable results would require a huge amount of planning and effort.

Technical issues

• Externalization of... specifically what?
• If quest/NPC data were to remain within the sector maps, each sector would need to be modified to account for every possible combination of quests and states, making the maps much, much harder to maintain.
• Others?

Aesthetic issues

• Random is OK, procedural is better.
• Balance! Are there elites in your starting sector? What about the sectors neighboring it?
• Others?

Implementation considerations

• The randomization routine would need to consider things like coast lines, road connections, terrain type (jungle, desert, urban, etc.) when choosing/placing the maps. For instance, a common system of road connections might be required so that sectors "snap" together like Lego pieces.
• Maybe only place vendors on maps with shops, vehicles on maps with garages/gas stations, doctors on maps with hospitals, priests on maps with churches, training bonuses on maps with the relevant structures, etc.
• Sectors could be given a "difficulty" rating by their authors (from 1 to 5 maybe), which might or might not be independent of enemy soldier selection/placement. Maybe a "population density" value as well (a count of the number of rooms, divided by some amount). 
• Others?

See also

• Can maps be randomized?
• 1.13 Map Database Project
• Changing starting sector and position
• Externalizing Mercs & Quests
• Big Maps Project
• Sector map randomization
• Tool Request