Switch the component into .sdk mode. Maybe in a Python 3 component you can then just use **kwargs, or even set defaults.
Otherwise, I know this works in Iron Python components: replace the first optional arg and all subsequent ones with *args, and then zip those together with the arg names from self.Params (or somewhere in the API to filter for ihe Input ones).
Any missing args are simply set to None by Grasshopper - your code within RunScript needs to work with this.