I'm all for modifying the themer applet to search for matched themes, or asking themes.org to enable contributers to add links to matched themes in other sections. But any form of integrated theme package is opening the way to abuse. People should be able to download a package and know what's included in it, and not wonder what piece of worthless crap the author choosed to add to its theme. You can always download another package. On the subject of themes most people want these to be simple to use.
Integrated themes are more modular from a user perspective.
By the way, sawmill comes with a basic theme that just uses the colors from your gtk theme. So if that's what you want, you can use that. And you configure sawmill from Gnome's control center, no one is expected to edit the lisp code unless they want to. You should look at the corresponding gtkrc file. That's what I did when I derived my theme from Xenophilia.