Why Great Eastern would make an accommodation ship, not a carrier

What useful Second World War role could SS Great Eastern have filled if she survived in like-new condition?

An accommodation barge; her volume would be useful, but low speed, heavy coal consumption, and a thin hull would make a combat conversion poor.

The hypothetical preserves Great Eastern into the Second World War in like-new condition and asks for a useful conversion. An effective carrier is ruled out because the ship would be slow, extremely coal-hungry, and lightly built by later warship standards. Those limitations would make an operational combat role costly and vulnerable. An accommodation barge would use her exceptional internal volume without demanding speed or protection.