dump all the parameters except for 0 and 1 for now
It seems that your first parameter is a multivalue parameter which return a semicolon delimited list of shapefiles. You will have to split that parameter on the semicolon and process each file in a 'for' loop. in fact, it doesn't even appear as a parameter in your original script, it is defined as a workspace and not featureclass(es).
Why don't you just run the existing tool in batch mode? (or can't you do that in arcmap? I can't remember)