I finally found time to write a script that allows simple import of others playlists. This script does not any fancy or crazy stuff, just replaces bunch of paths for games and cores in the playlist and saves it as a modified file. But this requires to setup a configuration file with rules, mostly a few options and all folders for each system.
Usage is something like (yes, it’s a command line driven thing again, no GUI):
./retroarch-import-playlist.py -o imported "examples/playlists/Arcade - A-Z Uncommon Arcade Games.lpl"
The -o imported will put the create file into the specified folder named imported. I mainly wrote it on Linux, but it should work on Windows I guess. The Readme explains what is needed.