Before the start of the season, I'd assumed that without a merge host, fastrack and RAP would share the left side of the queue with main on the right. Tickets/return times could either be checked by an entrance host or otherwise the merge host would be responsible for everything.
The current situation is just bonkers though - they're expecting main queue people who've waited however long to give way to the RAP guests. Good luck with that. I'd hate to be in the position of trying to merge in the main queue at that point, you'd just get abuse from everyone else. It clearly won't work on fireworks day - last year RAP and fastrack queues were out the building most of the day, and that's before they slashed capacity on the ride by closing the bag room.