IMO instanced housing if added should be exclusive to sea of clouds. That way people that want a house in their own little world can be off on their own little rock in the sky away from everyone else.

The neighborhood design we have with current wards is fine. The problem is that the plot costs haven't been adjusted for inflation over the years and as such its incredibly trivial to get the gil needed to buy a housing plot as a player. The rest of it is entitlement issues of people that either didn't want a small plot that was available because they didn't like the location of it or wanted something bigger that was already taken, decided they didn't want to put the effort into getting a plot when it was announced more were being added, or just feel like a house should be given to them then make arguments along the lines of everyone in NYC should have a house, just build more so everyone can have one.

I also wouldn't mind if Ishgard were eventually opened up as a new housing area but had things switched up so that players had to spend the time using crafting skills to actually build their initial home, at which point they can then customize it like the homes in other wards.