As Leon Rose prepares for his imminent takeover, Garden constant Allan Houston has emerged as a candidate for a front office promotion, a league source told the Daily News. The former All-Star, 48, is currently the GM of the G-League affiliate in Westchester and has been a Knicks executive since 2008, surviving multiple regime changes while being groomed for a larger role. He also served as the Knicks assistant GM before and during Phil Jackson’s tenure.