these are at least the reqs to be able to build everything:
Tactic 5
Trade 5
Spotting 2
Engineering 5
Leader 5
Persuasion 6
Tracking 4
Prison Management 2
Inventory Management 4
Pathfinding 4
First Aid 3
Wound Treatment 3
Surgery 5
Looting 5
Trainer 5
Weapon Master 5
per maryjoi (sp?) in the quick q&a thread