Hospitals can't survive without a cadre of doctors who have a real stake in the hospital's success. Most doctors can't survive in small private practice. But the obvious way to mesh their interests ? physician employment by hospitals or practice acquisitions ? is losing its luster in many corners, so a new strain of strategic creativity is blossoming. The goal: how to work together without living together. "More sophistication is coming to the market place," said Steve Messinger, a hospital strategist and managing partner at ECG Management Consultants Inc. in Arlington.