In order to promote a continuous open space or a subdivision design more compatible with existing topographical features or conditions or to reduce the length of road, curb and other public improvements, an applicant may voluntarily request in connection with subdivision approval that the individual lot sizes and setback requirements in the R-150 Zone be reduced to the next lower residential district, R-100, provided that the number of new residential lots shall be no more than would have been permitted had such reduction not been granted and approved, and provided further that the collective open space in the subdivision not on the individual lots be dedicated to the Borough of Paramus as part of and as a condition of the granting of any preliminary or final subdivision under the provisions hereof.