Any proposed communication structure and related structures shall be designed, structurally, electrically and in all respects, to accommodate both the applicant's antenna(e) and comparable antenna(e) for at least two additional users. The communications structure and related structures shall be designed for future rearrangement of antennas and to accept antennas mounted at varying heights. If the foregoing design for co-location requires additional antenna height beyond that necessary for a single-user installation or beyond that permitted above, the Board, in determining the acceptable design, shall balance the benefits and probability of co-location against any detriments resulting from such additional antenna height. If and when there are three or more users on the communications structure, the same shall be deemed a permanent structure and shall require on-site sanitary facilities conforming with all applicable laws, rules or regulations.