I think people are kind-of forgetting something in this discussion: "value" is set by the people that are buying, and for every collectable there are probably different rules. We can look to the classic car collectors for guidance here. With some cars (say, like the Model T) there are still tons of old-stock parts out there, so for a Model T to have extraordinary value requires that it has all OEM parts. Contrast that to a Tucker, where even the OEM used weird parts on some cars given the prototype nature.. however, documentation is always key. An excellent contra-example is in cameras. You could have a pristeen in-the-box Polaroid camera and a barely working similar vintage TLR.. guess what's worth more? It isn't the Polaroid. The TLR likely still is a functional camera (film is available). Polaroid film by in large is not available. It is sensible to me that limited modification to maintain an operational state wouldn't affect the collectible value much, especially compared to "not working at all."