Onions are just a small part of this that I use as the example, and you should realise it.
On your future new NA worlds, if they stop all housing for 3 months at the start, people who want to RP in a bar can just head off to Balmung with intra-DC-travel. On OC, no RP in bars, housing is locked out.
On your future new NA worlds, if they stop housing for 3 months at the start, people who want to make furniture and decorate can stay on their old worlds without penalty until housing is opened, then transfer over, no problem. We can't do this, we need to pull up roots completely for 3 months, or start anew and grind up our FC rank, and GC rank.
On your future new NA worlds, you have the chance to head over to any server, so don't need to leave all your friends behind. On OC we need to restart a new community, merging JP and NA playstyles, not having housing ties less people here. We need the people, but for that, we need access to all the perks of housing.
On your future new NA worlds, you will mostly have EW players who transfer. While on OC we mosly have sprouts who have left their EW mains on the old datacentres. You can't begin to imagine the disruption in this one.
Many more differences too.
What you will see in NA will be completely different to what we are experiencing now. And really, your investment in our data centre just warps what we need for no good purpose. It won't change what happens in NA in a years time.
We need housing in the old cities opened now, to make a community, to allow roleplay, to stock the marketboard, to let people decorate, to stimulate the economy and more.
Heck even to free up houses on NA. A lot of people, like me, have their old mains with house still idle and unused on NA, because no houses on OC, so no way I am giving that up yet. Have a house on OC and there is less need to keep on on NA. I'd likely give up my NA house as soon as I get an OC house, and that means a NA player can have it.
Old cities now needs to be FCFS as it's prior to 6.1, lottery doesn't exist yet, and that's fine, we just need the housing unlocked NOW. Ishgard for 6.1 can be lottery as in all data centres, we don't seek special rules there.
Worry about your future NA servers please, and stop trying to set your direction on the OC servers please, because what you will see in a years time with DC travel allowed will be completely different to us.
Edit: Transfer stuff over, you say. Meh, I would, Aether is locked to new alts, No mules left. and that doesn't address the bulk of the need, just shortages in garden and FC workshop.