As for your last point, we already have oil rigs and the like far out at sea, don't we? I don't know exactly how they work, but they show that it is at least plausible.
Evacuating 50-100 highly trained rig personnel is different than several hundred rank-and-file knowledge workers. Rig workers are paid high salaries because of the risks associated with working on oil rigs. We lost a close family friend to an explosion that occurred during a "routine" welding operation. Routine is quoted because nothing on an oil rig is truly "routine".
A fire alarm in an office building means everyone saunters outside. A fire alarm on a oil platform elevates everyone's heartrate. There is a not-insignificant chance that you're going to die. Mitigating these risks to the point that it would make sense for companies to utilize them for operational duties will be very difficult, not to mention expensive.
