I don't think it's possible what you are trying to achieve.
The parameter settings in runFn seems to contain only the map generation options in custom. They are also printed in the stdout:
config dict:
climate: temperate
vehicles: europe
nameList: europe
environment: temperate
I think it's meant for mods to react only in a specific configuration (i.e. only be active for american vehicles) and the parameters are read-only.
Would be nice, to access more of the user settings with that. How doug mentioned, many configuration settings can be accessed and modified with game.config. ...
However, some mods add a settings.lua file to handle settings for configuring the mod itself. (https://www.transportfever.net…ry/217-Settings-for-Mods/)
Sadly, there is no parameter window in the game mod list yet.