Running factorio in system mode but not in /usr/share/factor

[exi]

Hi,
I just found out that it seems to be impossible to run factorio in system mode under linux.
System mode meaning:
use-system-read-write-data-directories=true
in config-path.cfg

This is a problem as i am currently trying to make factorio easily installable/runnable on nixos, where /usr/share just does not exist.
It would be awesome if I could point factorio to its base directory via a command line parameter. That would allow me to just provide a small wrapper script to run it properly.

[prg]

use-system-read-write-data-directories is only used to generate an initial config if none exists already, but you can just specify different values for read- and write-data in the config manually if you don't like the defaults. You can tell factorio which config file to use with the -c option.