(grin)The PLUS of a two door is the air flow and need less exhaust fan to dry out during and after shower times.All I see in the change is your making the bath smaller and taking bath closet for master space. 

For other motor types, the increased pressure can actually cause the motor to work less hard, which reduces airflow to the rest of the home. 

There are usually laws regarding minimum standards for plumbing, air flow, and heating, fire safety standards, etc that are affected by the number of unrelated people renting part of the same dwelling.

I'd give more consideration to the end user interface... the devices, how well the rooms heat up, air flow, and thermostat controls.

To remain "cool" a heat exchanger requires a constant volume of airflow.

My contractor is urging me just to get a dehumidifier in the basement, open up these cemented in windows in basement for some air flow and put bleach on walls for mold but we didn’t discuss the foundation.Would appreciate some advice.Thanks and happy holidays!

This usually makes a significant difference, because the tenants forget to turn them on, and now it will automatically come on.You should also check the vent outlet on the side of the building or roof and make sure there is actually air flowing out.  

Can't say for sure in that exact situation, but experience has shown me that 9 times out of 10, freezing issues are associated with air flow/infiltration more than just poor insulation.

For that reason you also want proper venting in an attic which means under soft vents and roof vents to keep air flow.

I don't let tenants change HVAC filters because if they are installed backwards, they restrict airflow and can damage a unit.