Seems to be a practical solution at first sight ...however ...with todays construction environment I guarantee it would end up as a high maintenance operation with plenty of closures.
It would not be wide enough to take maintenace or emergency vehicles ,the ventilation and lighting systems would be unreliable or innadequate, and it would probably have a toll to cover maintenance costs(or budget overruns).
Oh yeah ..it would probably LEAK.
Why have I become so cynical in my old age .I wasn't like this in my youth?