You can edit your posts to go over the caps. Also they kinda had to have some form of registration system so that way your guests could attend. Including multiple chapels in each of the city states might have alleviate some of the registration stress but they'd have to commit more resources to make that happen. FFXIV developers always seem to go the cheap route either because they think they can get away with it or that they underestimated the appeal of their product similar to what happened during game launch.