Charles,
You should not have a problem with duplicate UID. I just pasted 346 instruments three times into the same document and no duplicate UIDs were created.
If you are talking about other data fields, then it is possible to create duplicate data in those fields.
But that aside, the best way to do this is to use Design Layer Viewports. All three people should be working in separate files. Then in a 4th file use design layer viewports to reference the other three files. Any edits would need to be made to the three original files, but the referencing file would automatically be updated when it is opened.
Each design layer viewport is it's own little space. You can not edit objects in the design layer viewport, but you can control visibility and it will allow you to open the referenced document from the viewport.
Kevin