If being reported AFK before the match starts is not a bug, I'd suggest running the macro and reporting everyone else as your normal practice anytime you're reported.
At least all the assholes who report you before the match starts will also be booted.

The squeeky wheel gets the grease.
If it's going to take a few hundred threads on the suggestion forum (from angry people who have been flagged AFK before the match starts) for the Developers/GM's to change the system, so be it.