Rain Noe has an interesting piece up at Core77 about adaptive reuse of an abandoned power plant by building new spaces within the cavernous main hall. He rightly refers to this as box-in-a-box architecture. I think that, for certain types of buildings, it’s a great idea.
Most adaptive-reuse projects center on how to get the interior layouts to match the new use. This can involve moving partitions, wholesale removal and replacement of partitions, making openings in bearing walls, cutting in new cores for stairs and elevators, and so on. The case of a building without a use that consists mostly of a huge open space is a rare one, although abandoned shopping malls often consist mostly of several connected huge open spaces. Creating usable smaller spaces inside of such large spaces is an interesting problem in design.
In case this seems pointless, remember that the energy, materials, and carbon involved in creating the old building will be wasted if it’s demolished. The old shell is still going to perform some structural work (resisting wind load, for example) and will still perform the architectural work of keeping the weather out. Having to build the new inner “box” is not as efficient as reusing old interior floors and partitions, but it still beats starting from scratch.