I suggest to implement the following feature:
Introduction of a reference count for used image streams in the previewfile.
When outputting individual pages as new previewfile then the count checks whether/which images in the questionable pagearea are used and only this/those will be embedded in the new previewfile.
When exporting some pages from a previewfile including lots of images to a new previewfile (using LLGSysconvert), the filesize for the new previewfile is almost as large as the filesize of the original previewfile (obviously the BLOB-list is not cleared). This causes unnecessary memory usage.