Proposed HVAC System vs. Baseline System

The proposed is easy - model what you are building. The baseline looks like it should be System 4. See the note under Table G3.1.1A - "Where attributes make a building eligible for more than one baseline system type, use the predominant condition to determine the system type for the entire building." Model the heating only space in the baseline with System 4, no need for a second system. While you do need to model a cooling system for the uncooled area you can simply set the temperatures in that space during the cooling season to ensure that the system does not operate. Make sure the temperature settings are the same in both models.