There's an easy fix that fills vacancies, is fair to candidates and empowers the electorate. When a vacancy occurs after the statutory 100-day period, too late to allow the voters to decide, authorize the city council to appoint an acting councilor to complete the remainder of the term, but bar that acting councilor from running as an incumbent in the next election as a condition of accepting the temporary appointment.  Then, in the next election, the voters can elect a new councilor on a level playing field, without some candidate enjoying the unearned advantage of incumbency.