Okay, so I recognize this is a big one. But I'm making this suggestion because this is one of my favorite plugins ever, because I think it offers to turn wordpress into an epic all-purpose INSTA-CMS. Here's where I'm at:
I find myself wondering whether your plugin would ever integrate with search. Currently, if I'm looking at a search archive and try to "narrow" by a taxonomy-item, it drops my search terms and just shows the taxonomy-based archive. But I know that WordPress can combine taxonomy-filtration and search-filtration: http://signsofsafetyusa.com/?s=sitting&category_name=reflections&tag=honesty
Since wordpress already has the machinery built in to integrate taxonomy and search in a query, I'm suggesting that this plugin also integrate search and taxonomy.
Here are the ways : (in order from most to least important)
1. Just like the plugin currently recognizes when there are cats and tags in the URL, it would recognize when there are search terms (
s=my+search+terms) in the URL, and preserve them upon the addition of a taxonomy term just like it preserves the cats and tags.
2. On the widget options, offer a "search (filtered)" checkbox. This would create a search bar at the top of the widget, that appended any entered search terms into the url/href, either after existing terms, or by appending/splicing the whole search expression (
s=my+search+terms&) right after the
3. Right under the 'add search term' box, create a list of already-searched terms, which, just like the list of taxonomy items, can be removed by clicking on them. This way, search terms could be added and removed fluidly just like taxonomic terms, creating the ULTIMATE CONTENT FILTRATION SYSTEM OF DOOM AND DESTINY. Ahem.
I recognize that what I'm suggesting would be a TON of work.
Let me know the realism/feasibility of the feature requests I'm making. If working on this would require some donation-juice, let me know and I'll poke around WP.org to look for donors on some kind of kickstarter-flavored effort.