Kairos Shen is returning to his old job as head of the city’s development agency – and Scott Van Voorhis is right there to welcome him. With a blowtorch. … Setting aside Shen’s obnoxious pension grab when he last left City Hall, I wasn’t a big fan of his previous “modern materials” mandate for new buildings in Boston. I’m not one of those traditionalists who want red bricks, bricks, bricks all the time. But I also don’t want glass, glass, glass all the time either.