I see the parameters framework working as follows (NOTE: I haven't finished designing it yet, so no guarantees :D):
On the Settings page, the module editor would add "parameters." Each parameter would have a Name (i.e. "UserID" or "CustomerName") and a Source (i.e. "Current User ID" or "Text Field Prompt"). Some Sources have no UI, such as the "Current User ID" source which simply pulls the currently logged-in user ID. Others, like "Text Field Prompt", would display a UI in the View page which allows the user to specify the value. Additional "Sources" could be installed by SuperUsers.
Once the module editor has configured the list of parameters, they can be used by the Query. Exactly how depends on the type of Data Source. Essentially, every Data Source gets a Hash Table containing the Parameter Name and the associated Value. The SQL Server Data Source, for example, would then prepend an "@" character to the front (i.e. "UserID" => "@UserID") and pass the Parameter Name and Value on to SQL Server. An RSS Feed Data Source (purely an example, no current plans for such a data source, but anyone could make one :D) could use the parameters in the URL instead.
I think what you're looking for is the ability for the module viewer to select additional parameters to filter the query by. I don't have plans to do this in "Saltspring" simply because I didn't think of it, but I don't think there's enough time to get it in for that version (I want to release it before I start at Microsoft in September :D).