Completely agree that the features that are not imported well or at all should be documented.
It is strange that you aren't able to "open" a single Word document. When you say "open", does that mean that you get an error message, that Pages crashes, that nothing happens, or that the file is opened with distorted formating?
How were the Word documents made? Which version of Word? Did they use normal.dot as template, and if so, has it been customized or is it a normal.dot with factory settings?
If you care to work on it, could you try a step by step test? First create a document from scratch in Word using the standard normal.dot template. Add just text - nothing more. See if that opens. It should. Then add features one by one to get to your "standard" Word document, until it breaks Pages.
In case you don't have Word, but you get Word files from other persons, and they all "fail" opening in Pages, my bet would be that they all are built on a template in Word that consists of some fancy formating, that Pages cannot handle. Complicated tables? OLE objects? Twisted Styles? Macros? A corrupted picture?