Since mid-2013, I had been working on a pack of Duke3D addons which can be easily run from within the EDuke32 launcher by using the grpinfo feature. The result is a collection of about 60 groupfiles containing about 670 levels, over 1.1 GB of data (uncompressed). It works really easily: It comes as an additional folder (“addons”) which contains all the groupfiles, you add -jaddons to your EDuke32 shortcut and see all the groupfiles in the launcher afterwards.
Please see the readme file for full details.
As of today, the project is finished! You can download it on the HRP website (scroll to the bottom of the “Download” section). Enjoy!