You could be able to dig tunnels and build stuff underground, like in OP1, like use the Earthworker as a Robodigger and make underground tunnels. These would be invisible to the enemy base unless they have units there (meaning you can build secret armies and they don't know what you're building until they surface) and certain buildings would raise or lower Morale depending where they're located - for example, residential units would raise morale if underground because the colonists are safer, but smelters would lower morale because of the pollution it causes in the confined area. Also, you can put mines underground to increase their productivity.