I don't think it's a matter of how long it will take to add an AH, but rather if he feels it's necessary right now. While Yoshida did mention an AH in his letters don't forget he said the first things he was going to work on were the UI and battle system.

Don't get me wrong, I want to see the wards demolished as much as the next person, however at the same time I can't argue that they're not working for the current population.