I think one of the best things the new adaptations would have going for them is that the new movies would be working with the end in mind. Whereas the first films were stuck not knowing which characters would end up dating, who would turn to the dark side, et cetera, et cetera, a new series would have everything laid out for it from the get-go. The filmmakers could map out the entire book series, separating weed from chaff in terms of what most needs emotional emphasis in the overall arc of the series.
And speaking of filmmakers, I think that that would be another huge advantage the new films would have over the old ones. I think it's likely the new filmmakers would have a much deeper respect and love for the series than the current ones do/did. At this point in time, Harry Potter isn't really taken very seriously by too many adults. Many of the Harry Potter cast members have never actually read any of the books, Alan Rickman and Michael Gambon included. Similarly, none of the Potter directors came to the project of their own accord, but were offered the series by Warner Bros. Literary critics are by and large dismissive of Potter's literary significance, about which I wouldn't contest them. Harry Potter isn't great literature. But that doesn't mean it isn't important. It's arguably the most important book of the past century, at least in terms of its overall cultural impact. That impact has yet to really fully permeate into the adult world though. That's not to say there aren't plenty of adults who don't read and like Harry Potter. What I'm saying is that only just now is there a generation coming into adulthood who actually grew up reading Harry Potter. (On a side note, I'm very interested to see how Harry Potter's influence affects my generation's fantasy writers.) Once all of the original film series has finished and the Potter hype has more or less died down, I think Potter's literary significance will more or less cease being debated and the series will gradually grow in respectability, at least as a children's classic. And in this more Potter-accepting society (although Harry will be far, far less hyped by this time), I think there will emerge a filmmaker who loves and understands the series in a way that only one who grew up reading the series could. And this filmmaker will see the original Potter movies and say to himself (or herself), "I can and will make better Harry Potter movies."
From that point, the stars will have to align a bit for the project to actually move into fruition. Enough time will have had to have passed since the original film series for a new one to justify existing. The studio--I imagine Warner Bros. will forever hold onto the Harry Potter rights--will have to be convinced that a costly remake of the Harry Potter series would be a lucrative endeavor. The director will most likely have to have earned enough clout from his previous works to push the studio toward allowing him to make the movies. And there might also perhaps be legal issues with Rowling's estate about a new film series. But I'm sure at some point in the future, of all these things will come to pass, and then a new Harry Potter film series will move into production. This brings me to casting.
The Harry Potter movies have become such a staple in most of our lives that I think we've forgotten what an amazing anomaly they are. An enormous cast of actors, many of whom were all children at the project's inception, has stuck with the same film series for eight entire movies. Nothing else has ever happened like that. (Even if the Narnia series successfully plows its way through a Last Battle movie, the series switches off to a new, younger pair of children every two books or so, a wonderfully fortuitous plot direction for Hollywood.) Successfully adapting Harry Potter requires an enormous time commitment from so many actors, most of them children that it's almost miraculous it's even happened once. Replicating that again in the future will be equally tricky. There are, however, definite places for improvement from the original series.
To begin with, Snape. Alan Rickman's Snape is not a good adaptation of the character. Yeah, yeah, I know. "WHAATTT?!!" you're thinking angrily, readying your metaphorical pitchfork. Look, I love Alan Rickman. Probably even more than you do. And yes, his portrayal of Snape is deliciously sardonic; his mere presence onscreen makes me crack a grin. And that's exactly the problem. Snape is not supposed to be lovable. He is an asshole. He is, in fact, very nearly evil. Let's not forget (spoilers spoilers) that the only reason Snape stopped casually murdering muggles with Voldemort was because of his childhood crush on Lily. (End spoilers.) Let's also not forget that passage from Goblet of Fire in which Malfoy jinxes Hermione's buckteeth so that they grow hugely out of proportion and Snape, surveying the crying little girl before him, says "I see no difference." Those, ladies and gentleman, are the words of a bona fide asshole! Sure, there's a black comedy to his response, but that doesn't change the fact that he cruelly mocked the physical appearance of a fourteen-year-old girl. (In fact, one must wonder if Hermione's purposeful buckteeth shrinking a few minutes later wasn't related to Snape's assholiness to her.) Alan Rickman's Snape never quite captures how truly despicable the character should be. He essentially is playing a comic role, and his portrayal never suggests the tortured emotion and nastiness that should be lurking inside. When the eighth Harry Potter movie is released next summer, I'm not sure if the "Snape's Story" passage will be able to carry nearly as much weight as it did in the book.
Alright so that said, who else do I have a gripe with? Rupert Grint has never quite been the perfect Ron. I can't entirely pinpoint why, although it think it might just be that Grint isn't as endearing as Ron should be. Retrospectively, I think Michael Gambon is a better Dumbledore than Richard Harris was. I guess if I wanted to get really picky, I should start complaining about how the guy who played Neville should've remained fat for his entire young adult life, but that just seems cruel.
But how about some praise? How about some parts that were cast so well that casting them in the new movies is going to be a most daunting task? Who can improve, after all, on Maggie Smith's McGonagall? Or Imelda Staunton's Umbridge? Not to mention the monumental task of finding a new Harry. It's almost eerie how perfectly Daniel Radcliffe represents the globe's collective imagining of what Harry Potter should look like. Plus, he can act (at least now he can). Finding a Harry Potter was hard ten years ago, and it will be equally if not more difficult to cast him again in the future.
Locations will also be problematic. I think Hogwarts has all been blazoned into our mind as this specific image:
