A very simple mod that mixins into the game to allow a modpack developer to define a default-server.properties in the root of the pack. This will then override the default creation of the server.properties file. The beauty of this method is that you only need to set the properties that you want to change by default in the default-server.properties as the games native loading will take care of the rest.
Create a default-server.properties file in the games root folder. If there is no default-used.marker in the local folder then the mod will attempt to load that default data in and inject it to the normal default creation of the server.properties... simples.
Why is your version number set so high?
That's a good question! the version number uses the incremental count of Minecraft releases as a major version as each Minecraft release defines a new major release for the mod.
Because of this, it means that our minor version is effectively our major and our patch is a combined patch and minor if you're used to how semver works. It's not amazing but when you're chasing a never ending target, this is about the only good way I've found to ensure there is never a version collision between different versions of the mod that are being actively maintained...
If you have any recommendations, feel free to let me know!...