This proposed new zoning law that you are considering sounds like big government over reach to me. I agree that zoning laws need to be periodically reviewed and updated but the fact of your proposed changes indicates to me that by incorporating your recommendations you will be making literally thousands of properties out of compliance, even after they received building permits and built approved structures.
The fact you will grandfather these makes no difference as you will require compliance if there are any repairs, remodeling, etc., done to them. How do they become compliant to the new forest agriculture development mandated acreage when they cannot expand their lots? This will put entire subdivisions out of compliance. What cost will they encounter trying to repair or reconstruct to current rules after hurricane damage?