Irrlicht Engine

If you're using models, you could hide the mesh's for the enemy pieces unless they're in a certain radius of your pieces/buildings...using a class for the pieces wouldn't be that difficult...

Mesh (pointer returned by loading the mesh - use it to hide/show the units)
Affiliation (Yours/Enemy 1 ...

What about saving the view of the map to a jpg/png/bmp format in the working folder directory, then loading that image as the image for the tab control (iirc already a property built into the tab control you can use right away)