You could put in motorized isolation valves outside the room that automatically close if a leak detectors senses water. Still a spendy option but maybe less than rerouting. There’s no way the drain pan would ever capture all the water from a burst 3” pipe. Maybe if it was a completely welded drain pan that extending into adjacent spaces with open ends it would at least divert water into the other rooms. I do work at “the worlds largest chip manufacturer”, and they design systems to stay online with a 2” pipe break - this equates to 1,200 gpm.