Things are looking up. There is life after all of this.
bash 2.05 is out; has been for a month, actually. How the hell did I miss that?
Anyway, I’ve just been hacking group completion into the code and have now also added service completion. These new features are available with complete -g and complete -s respectively.
Once I clean up the code, I’ll submit these to Chet Ramey for inclusion in bash 2.06.