It seems that
FolderMenu is a decent replacement (the RecentX tabbed dialog with MRU data is however much more developed).
It's written in AutoIt3, combined with XML. But the
FolderMenu code doesn't say much to me (I'm not a programmer, even if I have compiled a few C++ and Java/Swing applications). I'm not even sure the source code page I've linked to here shows all source code, and in worst case the code only covers it's own UI.
It would be interesting to understand how FolderMenu deal with ShellExecute or whatever it uses to access global MRU data. Unfortunately, in this case I'm not the "chosen one". :(
Apparently - it gets the job done.