So the results of my plugin review thus far are... fairly dismal. In the interest of spreading the joy, I added some brief notes to the software wiki page:
https://fedoraproject.org/w/index.php?title=Flock_2016_software&action=h...
In addition, I surveyed a number of additional plugins I found, most of which were designed only for registration for a single-location event, or a series of same, such as a specific repeating or traveling seminar.
If anyone has other specific plugins to suggest, I await your input! :-)