Localities which are authorized to accept voluntary cash proffers may also issue bonds under the provisions of the Public Finance Act and other applicable law including local charters, to finance improvements contained in the construction improvement program, to the extent that the costs of such improvements have been pledged by landowners as voluntary cash proffers. Authorized localities may pledge the proceeds of such proffers as a specific undertaking from which revenue is derived pursuant to Article VII, Section 10 (a) (3) of the Constitution of Virginia. The use of pledged cash proffers to finance improvements shall be limited to the improvements or class of improvements for which the proffer was originally pledged, and all or any part of the total amount pledged through the conditional zoning process may be further pledged by the locality to support repayment of any such debt.