I think they could get away with making these child versions and one older set of the trio (I personally would prefer 7th years versions myself, along with a Neville, Luna and Draco), but beyond that I really think the best bet would be to delve into supporting characters. I mean, the books may be called "Harry Potter" but I don't think anyone can argue that some of the supporting characters became more beloved and popular.
Doing multiple versions of Harry would hurt the potential of the line. One child version, one adult version would be enough.
I remember enjoying the first two movies/books, but it was the 3rd book that truly hooked me - the back story with Snape and the Marauders elevated the world building in a way that captured me. It was the third book, the one that seemed to really open up the world Harry lived in, that made me a fan.
There are so many interesting supporting characters, heroes and villains alike.