One thing I've been thinking about is: do all realms really belong to United Realms?
I mean, there're the Wish Realms (not just the Wish Enchanted Florest, since the existence of a Wish Peter Pan proves the existence of a Neverland Wish), people just like the others. There are other realms that we don't know yet, with other versions of the stories we already know.
There are also realms with totally different speeds. Have the Black Fairy servants come too? And the mermaids? Is there a huge sea where the people of Poseidon live?
Is the location "United Realms" a creation of the curse or are they really the places of the ancient realms that were transported to Storybrooke? Have people just been taken away and the kingdom is still there or has the kingdom completely disappeared? Have other worlds without magic been affected?
Was Regina's decision really good? I mean, there may be thousands of other villains far more powerful than their previous versions. Wish Zelena, for example, would never have had Robin and would still be the Wicked Witch of West. Wish Maleficent, would never have recovered Lily and could still be angry with Snow. Wish Ingrid would never have regretted it and Wish Arendelle may still be frozen. Wish Ursula never reunited with her father and never recovered her voice.
1. I don't think that there is a Wish Neverland, just a Wish Pan who happened to get sucked up in the creation of the realm (maybe he was trying to find Hook after he left, who knows?).
2. The Black fairies servants are all still children, maybe just 18 depending on the UR's placement but the Dark Realm isn't a realm of Story and maybe all the babies were brought to Storybrooke between 622 and 701, the sea where Posiedon is from is in the FTL so it probably did get brought over.
3. I think that the locations were brought over to Storybrooke, I don't think there are any worlds without magic, ("Flower Child"), and even the LWM seems to be getting it back.
3- In Season 2, in the episode where Daniel is revived by Whale in a conversation between Rumple and Jefferson, Rumple says something like "Your hat can only go into worlds with magic, I want to go to a world without magic." That is, there are worlds without magic. Besides, I do not see this being impossible, after all, the World Without Magic has already come about having magic.