They need to be predefined inside settings. You are going to explicitly map the calling query string parameter with an xsl argument.  

HttpRequest.QueryString is of type NameValueCollection, so it would be easy to code.

I don't see any benefits but maybe I am wrong. Can you give me a use case? Contact me at xmlmodule@gmail.com, I am interested in every idea.

Ok, I did not think about this scenario before. To be honest, I did not even believe in a need for external xsl scripts and I was near by to remove them. I did not.

The current implemetation of parameters do a bit more than passing through querystrings. You can define static parameters or pass dotnetnuke and user properties into the script. So if the module passed through every query string, it would interfere with the other parameters and  might break the module.

Xml module will support IPortable, so you can export/import your settings. This will help during setup, but it doesn't help for maintance.

I have bad feelings in having indiscriminate pass through parameters and I am not going to add them for the upcoming release.  But I will not totally reject it, I will think about it again. It would be helpful if other users of the xml module would share their thoughts about this topic.