Switching stylesheets based on arbitrary path elements (arguments)

I am using Drupal 4.7 with CCK and pathauto (and thus clean URLs). I am using a heavily customized theme based originally on the Spread Firefox theme.

Right now I am using customized template.php and page.tpl.php files to display particular templates (page-[content-type].tpl.php) depending on the content type. Since I'm using pathauto, these don't appear as "node/nid" (although you can still go to those addresses) but as the arbitrary name of the page (e.g. http://example.com/whatever).

What I want to be able to do is to tack on something in the URL to serve users the SAME template with a DIFFERENT stylesheet. Moreover, I want to be able to have MORE THAN ONE of these.

So if someone were to go to http://example.com/whatever?print=y or http://example.com/whatever/print or something of that sort, one would get print.css rather than the default theme and Drupal stylesheets. And if one were to go to http://example.com/whatever?silliness=y or http://example.com/whatever/silliness, one would get silliness.css.

This is basically a "stylesheet switcher," except that I want to be able to control it through the URL, and I don't want it to set a cookie (as most switchers do) because I only need the alternate stylesheet for that one page.

1. I started by looking at the print module but this does both more than and less than I want.

- It does a bunch of printer-friendly formatting and moving around (such as with the links), which is great, but more than I need.
- It forces you to use a print.tpl.php template -- I want to use the SAME template for EACH given content type, each of which has a different template. This would mean I'd have to have one single print template for all content types, which isn't going to work.
- It only gives you the option of one alternate stylesheet (print.css).

2. Then I tried using $_GET with the method outlined by eliza411 in this post. This worked great, and I would still be using it if I could be. Except that once I upgraded CCK to the current version (I had a pre-fieldgroup version) none of those links worked anymore. I can't explain why upgrading CCK broke these, but nothing else about my site has changed. Now if you go to whatever?printme=y it ignores what it should be seeing within those PHP if tags -- so the alternate stylesheet never gets loaded, and everything looks exactly the same.

If anyone knows what might of happened there, I'm all ears -- because that was really the perfect solution.

3. I checked out the very promising-sounding handbook page on "customising the full page layout and sections based on path." This seemed to fail for a number of reasons:

- The arg()s don't seem to really work with clean URLs in place -- although I confess I don't understand the concepts of the arg()s too well
- The things I want to add to the URL are arbitrary and don't conform to an existing page. So unlike going to /admin/blah or /node/blah or taxonomy/blah, I want to go to (the equivalent of) /node/18/blah, where no page exists. It doesn't look like this method works in this way.

I tried each of the suggestions on that page and in the comments but none of them worked.

Now I'm at a loss. This seems like it should be relatively easy -- switch the stylesheet based on something in the URL -- but maybe I'm deluding myself. I liked the $_GET method because I could actually switch out many different parts of my templates based on that value, so I could easily turn off the default style-loading of Drupal and load only the print stylesheet, and also insert a link (as eliza411 does) back to the default page. Alas, that method no longer works for me.

Any ideas?