If they were to remake the show it would have to be relatively close to how the series really began. That means not jumping straight into the continuity of NuWho, which I believe would be a mistake. This also means they need an older actor to play the US First Doctor, and not go straight in with a Tennant or Smith-like Doctor due to their popularity.
With that in mind, it shouldn't be a Hartnell-esque archetype either - it wouldn't be the best move to copy An Unearthly Child word for word. The opener would probably be a bit darker, with the Doctor being a lot more morally ambiguous.
I think casting someone like Willem Dafoe as the Doctor could provide the same level of sinister behaviour that Hartnell had, but also have a gentle nature too... Not to mention he is an exceptionally talented actor as well. He's also 58 so he's even older than Hartnell, but looks really good. (and bless Hartnell, but he did look older than his years.

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There would be the cliche high school setting in mind as well... which would probably lead to some Smallville esque settings and guitar music in the background... so for Susan, it needs to be someone who is young, but mature. No Disney stars or whatever. Ugh. I say... Ariel Winter (Alex in Modern Family). She has the geeky stereotype down, and I think she's very talented. With a full on dramatic role as Susan, I think she'd be brilliant.
Ian and Barbara... I'm not so sure. William Russell is pretty much irreplacable as Ian, so I think taking a different angle on the characters would work well, if not fully replacing them with different characters. I think Colin Ferguson could make a great Ian though. I watched Eureka quite a bit when it was airing and I think he'd fit the part, even if they have to give him the background of a US marine.
Barbara... I'm not so sure. But from the top of my head, I'm thinking they'd cast someone fairly good-looking, perhaps older rather than younger. Well that's what I'd do.
I think it could be interesting to say the least... not worth an automatic veto if they treat it with the right level of dignity and respect, and make the series a bit darker, a bit more serious much like the Hartnell serials, enough to stand out against the UK series.
It could also make a cool crossover episode for the UK series. Twelfth Doctor, Clara and Danny go to parallel universe and bump into the Twelfth Doctor, Ian, Barbara and Susan who are struggling to get back to 21st Century America, etc, Coal Hill school background shared, etc, "I miss Susan" etc.
As long as they don't change the TARDIS though. That is crutial IMO to the series being fundamentally recognised as Doctor Who.