Doesn't sound like it would be a good fit for the way I study. And it seems to me to ignore the central ideas of using a Leitner system, but different people have different study needs. Perhaps I'm just not clear on how this would be used? ???
It sounds like it would be easy to achieve some (most?) of the functionality by just having a checkbox in test/learn (in the menu? in options?) that would mark the test/learn window as "stays on top."
As for having multiple "reminder cards", to me that sounds really hard to do! But maybe a way to export a single card to the clipboard so it could then be pasted into one of the various "post-it notes"-style applications that exist?