The installation of Neverwinter Nights by Lutris needs the following files:
nwclientgold.tar.gz
nwclienthotu.tar.gz
English_linuxclient169_xp2.tar.gz
All together, it’s a ~530MiB download.
For ./play.it scripts, I built alternative archives:
http://www.dotslashplay.it/ressources/neverwinter-nights/
nwn-linux-common.tar.gz
nwn-linux-1.69.tar.gz
For ~6MiB these archives provide the exact same files than the Bioware ones, I only removed duplicates that are already included in the GOG installer.
Feel free to use the ./play.it archives in the Lutris installation script, either by linking to my server or by hosting them anywhere you like.