Not sure if that counts (since it would be technically still be limited access, I guess...), but I was always curious to see what the Milvaneth Sacrarium in Ul'dah looked like from the inside and was always hoping that it would end up being a second possible venue for the Eternal Bond ceremony. (Maybe lore-gurus are going to bash me over the head now because that place isnt supposed to be used for that sort of thing, but I still wish we could get married not only in the Twelve Woods but also in other cities and that seemed like a possible prime-spot in Ul'dah to me.)

That being said: The chapel used for the Eternal Bond Ceremony is quite a beautiful place aswell and while I get that its supposed to be "special", it would still be nice to just be able to walk in there and take some more screenshots of the whole water-area, that you can only access while setting up your own ceremony.