The above is the basic layout for a map with skirmish AI.
Before you start to add any objects to your map you should include the SkirmishAI players. In WB menu go Edit>Edit Players List. The players list in the new window should include [neutral] only. If you have already placed objects on the map then their factions are listed in the players list, in most cases it's the civilian faction (for shrubbery, structures, etc.). Click 'Remove Player' to remove all factions from the list. When a message appears saying 'There are
n objects using this team. Are you sure you want to remove it?' click 'Yes'. When you removed all factions click 'Add Skirmish Players'. If you placed faction structures on the map before you added the skirmish players all these objects on the map must be manually re-assigned to their original faction. This is done in the 'Object Properties' window under 'General' > 'Team'.
Some details:
The base areas must be big enough for the AI to build the additional structures when player chooses hard AI. In WB under Civilian > Structures you can find an object called 'TempBuildingSize'. Use it to layout the base area sizes on the map. The base area is made of an inner perimeter and an outer perimeter. The area outside the base areas are encompassed by the 'CombatZone'.
The naming is always 'InnerPerimeter1' and 'OuterPerimeter1' for player 1; 'InnerPerimeter2' and 'OuterPerimeter2' for player 2, etc. and 'CombatZone'.
OuterPerimeter:
When enemy units breach the outer perimeter of an AI-controlled base the available units address the threat. Don't create an outer perimeter too big nor too small because the AI may react too soon or too late.
InnerPerimeter:
When the inner perimeter is breached the AI drops everything to address this threat. The inner perimeter shouldn't be much larger than the base area itself. However, if there is a choke point or some other tactical advantage some distance from the base, it makes sense to define the inner perimeter to include this point.
CombatZone
Incursions into the combat zone signal the AI that the stakes of the game have been elevated. Every map has only one combat zone.
Player Start Points
It's the point on the map where AI places the command center. And the AI measures it's build radius from this point. If the AI build faction structures at wrong places, on roads or railtracks or on top of supply piles for example, move the player start point around 'til the AI does fine. It's much easier than do rework part of the map.
Waypoint paths
The waypoint paths define the base entrances and every base got three of them named 'Center1', 'Flank1', 'Backdoor1' for player 1; 'Center2', Flank2', 'Backdoor2' for player 2, etc. The waypoint paths always lead
inside the respective inner perimeter of a base area.