Friend.... i see the next issues on your request....

1.- While is true Wards at Ul'Dah are the most congested cause most (for not say everyone) set their retainers there while others are empty.... imagine what could it become of it if they conect all wards!

2.- SE has made clear their intention to make people to move to other city states and not remain stuck on Ul?Dah only... and actually the previous point (#1) is a reason for this.

3.- Im sure not everyone loves Ul'Dah as their home .... as much only cause everyone gathers there so is easier to shout/get repairs/sell stuff

I think the key for this is not unify wards or change whole system into an Ah like at XI, but more really something like make retainers more useful, lets say like make them go other nations do our shoppings at certain times or smething alike.... like you go contact your retainer in Ul'Dah and you have other things to do than go check Limsa Lominsa wards... well sent your retainer check out for certain items you list to him.... watch that like a more an advanced "Seek item" function they already have.