I can control the data sent to the fields. All fields on the deafult search allow you include/exclude in search results. I Suppose this is the default "drilldown" options.
I tried
<link>http://whatever
<a href="http://whatever"
The default search won't let you click the link, it just lets you filter on that field, is there an override to this?
You will have to build a dashboard and configure the drill down to open the URL value of the field.