A rendering of the proposed redevelopment of the Centennial building on Euclid Avenue. The historic Union Trust building in Downtown Cleveland could be reimagined as workforce housing under a redevelopment plan that’s been securing public financing in the past few months. The mostly vacant, 1.3 million-square-foot building, renamed The Centennial, at the corner of Euclid Avenue and East Ninth Street would be home to more than 860 apartments. Plans also include some retail and office space. “This is the missing tooth in the center of the mouth of the smile on Euclid Avenue,” said Tom Mignogna, a senior development officer for Millennia Companies, which is leading the redevelopment.