In my customised version of Singapore2 I have successfully added an axis freight train that DCG will target in allied forces objectives.

 

But how do I get DCG to recognise a base camp I have added as a target?
 

 

What I want is for DCG to see this area and buildings as a location and a possible target for allied forces to either destroy or capture.

And can I make this a "supply point"?

Waggon8 or the Radio Trucks trigger attacks pretty well.

As Nephris said, if you put juicy targets at the location, DCG will target it.