At least it would be possible to add the missing parts when (and if) the originals are 'discovered' later.
RE: the question about building a 5-footer replica: anyone attempting one is faced with building it from scratch like the original ILM modelers did as there is no kit for it. There isn't even a blueprint in an integrated form, though all the basics can be found here (and probably elsewhere.) Maruska has constructed a highly accurate 3D "form" model of the 5-footer (that is, less external details.) Though modern techniques have leveraged the ongoing research & documentation efforts to create needed components (for example, there are some parts available for purchase from 3D printing markeplace Shapeways - again, the efforts of another RPF member - at the 308 shop.)
So short answer, there is no kit for a 5 footer. Realistically, just how many folks could afford or even accommodate a displayable 5-footer? It must be made from scratch.
R/ Robert