I agree with everything Chris said just now.
Stop worrying and simply use Radiant. Use hierarchies, nested menus,
deep
URLs and good, usable navigation patterns. Make your visitors happy.
While
doing that, simply code towards good SEO practices on the way. Spiders
won’t
mind how you organized your site. Use “description” page parts for your
pages and render the meta tag in the layout. Use nice titles and
readable
slugs.
After you’re done, you can also create a sitemap for your site. There is
vanilla Radiant way and there is a plugin, if I’m not mistaken. Search
the
archives.