I don't think this completely resolved Ann's issue. I believe the idea is for the admin users to be able to embed a link to another content item from within a user-defined paragraph in the content editor. This would require the ability to select a content item (instead of just a page) in the hyperlink dialog, or at a minimum, the ability to specify a query string to be passed to that page, such that a custom widget on that page could use that query string to pull up the desired piece of content (using something like your code sample). It seems that you could accomplish this by manually typing the entire URL, but our admin users would never get that, and then you're stuck with an absolute link that includes the domain of the the server and needs to be updated upon migration.
As an example, I would like to embed links to definitions of terms from various places within generic content. These definitions exist as other generic content items. Right now it seems we would have to create a unique page for every term that we want to link to. Is there a better way to do this, or additional capabilities that will be available in the RC or final release?
I didn't completely understand the "custom selector" bit... maybe that helps solve this problem?