This all sounds fine to me. To sync stuff up after the event I would recommend writing a small script that zooms through your read write categories and then makes API requests using our JSON API to create the topics / posts on the master.
I definitely recommend strongly against having any kind of merge topic scenario, it will be full of dragons and not worth the effort.
Did you try anything for the same ?
I am into a similar thing where I need to take discourse offline with sync.
I have a master server and I will be having more than 100-200 slave instance. Slave instance can be online/offline but will be used by users. But whenever an offline instance comes online it should be able to sync with master server without creating conflicts and all update all the latest data. I do not want to create any code related changes as discourse keeps updating itself quite often and don’t want to break instance due to code changes.
I am thinking of tweaking postgresql to some extent. Other files related data can be synced using syncthing. But updating postgresql data is something which worries me because if i directly sync master data then the work done by offline user will get erased after the sync. How was your experience writing scripts for the same ?