Well, although I don't know that it would need to be quite that different - the nature vs. nurture argument gets involved there - the different personality is almost part of the point.
I do, in fact, have some ideas for And Then What, but they're a lot less specific, enough so that I didn't think I could continue to write in outline form without narrowing things down first. (There are also a few things I don't have specific ideas on even within the existing outline; some of them should be easy enough to spot, and any suggestions are appreciated.)
For starters, I'm not sure how old Harry would be when they found him, physically speaking. I believe it's "Peter Pan" canon that infants can become Lost Boys (I recall mention of a mother whose baby carriage rolls away while she is conversing with a neighbor), and that they do grow to independent childhood (since there are no infants among the Lost Boys we see), and Peter himself could be as old as twelve some of the time - so there's room available for Harry's being anywhere from still one year old to the full eleven he should be.
However, part of the idea I had is that although they would eventually succeed in persuading Harry to return to the larger world and go to school (and in explaining what "school" is to the Lost Boys who hadn't heard of it, and persuading the ones who had that it wasn't so bad after all - probably relying quite heavily on the fact that he would be learning magic), and he would grow and age (and mature) normally during the school year, they would be forced to agree to his returning to Neverland over the summer... and he and the other Boys would have to deal with the fact that he was aging and growing, but the rest of them were not; there's room for conflict in that, on both sides of the divide. In order to make the most of that possibility, he really shouldn't be older than about six, and I could see argument for his being as little as three - old enough to have the physical proportions and so forth to walk, talk, get around (and grow physically fit and able in other ways), and take care of himself to the extent that the Boys do, but young enough for the age difference at Hogwarts to remain obvious for all seven years. (And young enough that, if desired, he could potentially return to be a Lost Boy permanently even after the seven years were done.) However, the younger he is, the harder it is to make things work on the Hogwarts side of things.
As far as "different personality" goes, part of the idea is that Harry would in fact come to the wizarding world with the mindset, worldview and general background of a Lost Boy. I have some ideas of what that incorporates, but not enough to really be concrete (beyond a general "not receptive to the concept of discipline"), so I can't readily write his viewpoint and reactions yet; likewise, I don't yet have a clear handle on the minds and viewpoints of any of the people who would be reacting to him.
In addition to the social conflict from the age issue (too young at Hogwarts, increasingly too old in Neverland), there's also the possibility that as Harry does grow up, he might lose the mindset of a Lost Boy, and potentially some of the things which come with it. (Such as the ability to independently fly, which I do think could make more of a difference than you seem to expect; for one thing, how would it affect Quidditch? Would he even be interested in playing? If so, would it be for the same reasons? Would he even be allowed to play for a House team, given his physical age?).
There's also the possibility that other people from Neverland might come out to visit (Peter in particular), and that other wizards might track Neverland down (possibly by following Harry home, or simply exploiting the "follow a post owl" approach which is the main plot hole in my existing outline), and the likelihood that the wizards who had made the visit and discovered the existence of Neverland would themselves want to learn more about it; interesting fallout could arise from any of those. I don't have anything specific there, however, because figuring any of those possibilities out would require knowing the context in ways which I haven't developed yet.
Beyond that, I thought I had more (and more specific) ideas last night, but if so they seem to have faded; I discussed this to some extent with one of my brothers at the time, and once he wakes up I'll see if he can jog my memory.
(Oh - and no, I don't think Tinkerbell as a house elf works, if only because that would imply that other house elves should also be able to shed pixie dust and let people be able to fly...)
I do, in fact, have some ideas for And Then What, but they're a lot less specific, enough so that I didn't think I could continue to write in outline form without narrowing things down first. (There are also a few things I don't have specific ideas on even within the existing outline; some of them should be easy enough to spot, and any suggestions are appreciated.)
For starters, I'm not sure how old Harry would be when they found him, physically speaking. I believe it's "Peter Pan" canon that infants can become Lost Boys (I recall mention of a mother whose baby carriage rolls away while she is conversing with a neighbor), and that they do grow to independent childhood (since there are no infants among the Lost Boys we see), and Peter himself could be as old as twelve some of the time - so there's room available for Harry's being anywhere from still one year old to the full eleven he should be.
However, part of the idea I had is that although they would eventually succeed in persuading Harry to return to the larger world and go to school (and in explaining what "school" is to the Lost Boys who hadn't heard of it, and persuading the ones who had that it wasn't so bad after all - probably relying quite heavily on the fact that he would be learning magic), and he would grow and age (and mature) normally during the school year, they would be forced to agree to his returning to Neverland over the summer... and he and the other Boys would have to deal with the fact that he was aging and growing, but the rest of them were not; there's room for conflict in that, on both sides of the divide. In order to make the most of that possibility, he really shouldn't be older than about six, and I could see argument for his being as little as three - old enough to have the physical proportions and so forth to walk, talk, get around (and grow physically fit and able in other ways), and take care of himself to the extent that the Boys do, but young enough for the age difference at Hogwarts to remain obvious for all seven years. (And young enough that, if desired, he could potentially return to be a Lost Boy permanently even after the seven years were done.) However, the younger he is, the harder it is to make things work on the Hogwarts side of things.
As far as "different personality" goes, part of the idea is that Harry would in fact come to the wizarding world with the mindset, worldview and general background of a Lost Boy. I have some ideas of what that incorporates, but not enough to really be concrete (beyond a general "not receptive to the concept of discipline"), so I can't readily write his viewpoint and reactions yet; likewise, I don't yet have a clear handle on the minds and viewpoints of any of the people who would be reacting to him.
In addition to the social conflict from the age issue (too young at Hogwarts, increasingly too old in Neverland), there's also the possibility that as Harry does grow up, he might lose the mindset of a Lost Boy, and potentially some of the things which come with it. (Such as the ability to independently fly, which I do think could make more of a difference than you seem to expect; for one thing, how would it affect Quidditch? Would he even be interested in playing? If so, would it be for the same reasons? Would he even be allowed to play for a House team, given his physical age?).
There's also the possibility that other people from Neverland might come out to visit (Peter in particular), and that other wizards might track Neverland down (possibly by following Harry home, or simply exploiting the "follow a post owl" approach which is the main plot hole in my existing outline), and the likelihood that the wizards who had made the visit and discovered the existence of Neverland would themselves want to learn more about it; interesting fallout could arise from any of those. I don't have anything specific there, however, because figuring any of those possibilities out would require knowing the context in ways which I haven't developed yet.
Beyond that, I thought I had more (and more specific) ideas last night, but if so they seem to have faded; I discussed this to some extent with one of my brothers at the time, and once he wakes up I'll see if he can jog my memory.
(Oh - and no, I don't think Tinkerbell as a house elf works, if only because that would imply that other house elves should also be able to shed pixie dust and let people be able to fly...)