New building lots established by subdivision shall be created by dividing an existing lot by a single straight line drawn at a right angle to an existing property line. Variances from this rule may be permitted by the council, which shall consider, but not be limited to, the following factors: compliance with the comprehensive plan, Chapter 18.05 BAVMC, preexisting property lines, town streets, natural topographical features, natural obstructions, and impact upon adjoining or surrounding lots and buildings.