Kevyn, as it stands I would recommend that you consider using "transfer Libraries" with your editor to pass different Project/timeline versions between you.
Simply make a new Library, then select the Project you'd like to transfer and use the "File -> Copy Project to Library ->" command to make the transfer Library...
I basically agree with this, however what about first copying the project to a transfer event, then moving the event to the transfer library? Is that still necessary? We used to always recommend that to avoid several problems, but I don't know if it's still needed.
Sam Mestman discusses this from 06:30 to 11:00 in the below video. He demonstrates it on a Lumaforge NAS but it's not unique to a NAS. "Final Cut Pro X Virtual User Group #7":
If a transfer *library* is used that can work well if all media and cache are external. I would recommend the library always be ZIPed before uploading, downloading or even before copying to another hard drive. It is internally complex and the single ZIPed file makes the upload/download/copy go faster and more reliably. ZIP also embeds a CRC check to ensure the recipient either receives a good file or gets an unambiguous error when unzipping it.
Also, based on Dave's research, after fixing the other problems with media files lacking file extensions, the only problem with the project XML is a single .PDF file being used as an image. That is "Bud%20Farrell%204.pdf".
Today I fixed that by simply renaming that one file in the XML to "Bud%20Farrell%204.jpg". The XML seemed to load and the project ran OK (at least without any media). That may avoid deleting the other lines in the XML. The XML import still got those other lower-severity warnings, but I'm not sure that's related to the main problems.
Upon reviewing supported still-image media types in FCP, I don't think PDF is officially supported:
PDFs seem to import and display, at least on the few tests I did, but if the PDF media file is missing the XML will not load.
PDF is a complex file type with many different versions. Even if it was somehow supported by FCP I would not use it myself for an image because it seems inherently prone to compatibility issues in an NLE. So I've never encountered this before myself.
However FCP should not reject the entire XML just because a PDF is listed and doesn't exist on disk. Due to the apparent non-support of PDF in FCP, it's possible the fix might be to disallow importing PDFs.