You are welcome to try the utility I have written. It is a command line app that I wrote in C#. I actually use it with other scripts where I pass the relevant info via cmd line, but you can use it in fb2k with foo_openwith as well.
You can find it
hereIt relies on you passing the title of track 1 for an extra layer of accuracy so that makes it much less elegant than a no-kidding fb2k plugin. Be gentle, as this is the first thing I have written in C# (app was previously Perl) and I am open to suggestions, although I am not sure I am capable of making it happen yet. The included .htm file has the command line I use with foo_openwith. Let me know what you think.