The magic in those old shows, if indeed there is magic, is the cast. Those actors created those roles and can never be replaced in anyone who has ever seen them. Like The Little Rascals disaster a few years ago, you cannot simple replace a set of characters and have anything good come out of it.
Sorry, but I have to disagree. Coming from a professional actor, that's saying something. Yes, the cast is important. But so are the scripts and all the other elements that go into the show. There are well over a dozen film versions of Hamlet, with different actors in the cast. Some were better than others, but you couldn't say "nothing good came out of it".
Most sitcoms are crap. But then, most of everything is crap. Chances are if they were to do a remake of Bewitched, it would be crap. But chances are that if the same creative team were to create a whole new sitcom totally from scratch, it would still be crap. Given how old Bewitched is, they could just as easily come up with a "new" sitcom based on the same premise with a new name. Or, they could do the classic TV switcheroo and do a sitcom where the husband has magick powers instead of the wife. There's a long history of such reversals.
McHale's Navy lead to
Broadside, a failed attempt at doing the exact same show, except about WAVES.
Welcome Back Kotter lead to
Head of the Class, with underachieving sweathogs replaced with overachieving IHP students.
The Beverly Hillbillies lead to
Green Acres.
Mr. Ed lead to
My Mother the Car.
Or, you could make a case that
Charmed was merely a "prequel" to
Bewitched, about a re-named Samantha and her two sisters before Sam married Darwin (or Durwood, or whatever Sam's mother called Darrin). For that matter,
Bewitched was little more than
I Love Lucy with the twist of making Lucy a with and giving Ricky a different name, accent, and job.
Frankly, I'm more pessimistic about the chances of this being a success because the two writers have no sitcom experience. Sitcoms are very, very different from feature films. Just because they wrote a few good romcom movies, like He's Just Not That Into You, doesn't mean they can write sitcoms. Their only previous attempt of note at a sitcom was
Opposite Sex, which lasted 8 episodes. There's a chance that this might not suck, but I'd say the chance is small. It sounds like just another project for pilot season that will never be aired.