Not long ago, people on the forum were looking for a way to consolidate the QGIS project and related layers into one place. As no such tool existed, the discussion quickly turned into a thread full of wishes and feature requests. A little later, I was faced with the same task. Fortunately, in my case, the project only had vector layers in Shapefile format, so I quickly developed a simple and somewhat suboptimal plugin.
Now that I have more free time, I am slowly improving the plugin. I have already implemented:
support of file-based vector datasources
support for native database providers (PostgreSQL, SpatiaLite, SQLAnywhere)
layer processing has been moved to a separate thread, and the tool no longer blocks the main QGIS window
initial support for GDAL rasters
On the TODO list:
support for all vector data providers
finalise support for raster layers
provide the user with a choice of vector data format (Shapefiles or SpatiaLite database)