A feature I think would be very handy to Hugo and the community is a dedicated theme config file (or at least the ability to have one). Right now Hugo does allow for multiple config files using the --config command, however, the biggest drawback is that you have to continually re-declare the configs using --config each time you serve or build the Hugo files – it’s not stored.
Also, one of the my ongoing complications is to have easy/live theme switching, this is mainly because each theme has it’s own config options – you can see this with any theme you download from hugo themes.
If we had the ability to use both the standard config.toml and a dedicated theme config like theme.config.toml without having to manually declare it, we could eliminate the need to continually replace or redirect config files. New users could adopt themes much faster and with less errors, and more advanced use cases would be menus that pertain to that theme (ie. a one page menu vs multi page menu).
Right now my automated approach to this is each theme has a theme.config.toml | yaml | json file in the theme/data/ folder, but this comes with it’s own headaches and drawbacks.
