Expanding the World Map, Nodes, Skirmishes and Events

Does anyone have any good resources, information etc. on expanding the World Map’s Nodes, Paths and Events safely?

I know that certain aspects are tied to the “save data”. Is there any room for expansion or will any slight modifications require a complete reworking of the “save data” structure?

On a side note, what are the conditions for enabling skirmishes? Simply specifying the “clear” map doesn’t seem to cut it.