Thing is, I'm probably more willing than most to give some leaveway. Such as I don't believe it has to be a period piece. BBC's Sherlock shows that you can modernize and keep the spirit of the original alive. Very little of who the the characters are in the books are changed for that show (the same cannot be said for Elementary). I think part of the reason pulps are experiencing renewed interest is because history has come around to where they are relevant again. Wars in the recent past (how many of the pulp heroes were veterans), war and unrest overseas, distrust and gulf between the wealthy and the poor, fear and unease of crime and violence on our doorsteps... when you see the news of the latest mass shooting or terror attempt, it seems as if something ripped out of the pages of a Spider or Operator 5 novel. And, I think the need for heroes to believe in. To see pulp adventure played out on the screen in the modern age, one just needs to watch tv. Doc and the rest are in there almost every day of the week: NCIS LA, Bones, CSI, Person of Interest, Arrow, Hawaii 5-0. The Mission Impossible and James Bond movies all have the necessary elements of a good Doc Savage movie and even some of the right attitude.
And, I'm willing to concede that actor-wise, to allow the pulps their hyperbole in the character descriptions. You're not going to get someone that is going to look like most of the cast, they are of such unique and disproportionate attributes. And, everyone has their own unique version in their head. Such as Renny's huge hands. One thing I liked about the George Pal version was how in the first scene we see of Renny, he's wearing work gloves. I thought it was a clever bit, drawing attention to his hands even though they aren't noticeably large. However, I do think the cast of the five, as a whole they should be a unique looking group, easily able to tell one from the other and striking as a whole.
As much as the 1970s Doc Savage movie is panned, there is one scene where it got it right: the fight on the boat. From Long Tom having on his person a cigarette holder that's really a laser to Renny punching straight through a chair to the crook using it as a shield, that part really had me cheering. It would be kind of neat if we see some attention paid to the fact that each of the five has their own fighting style and not just a mindless choreographed scene where everyone fights the same. Another movie that I think got the right sensibility down at least in one scene is Iron Man 2. What almost stole this movie was Happy Hogan in that we see him as a capable character and hero in his own right. But, he's not a super hero. When we see him and the Black Widow go against some guards, he chivalrously leads the charge and ably fights the one guy, punching him out as a capable boxer would. However, while he's punching that one guy, we see the Black Widow moving quickly and taking out multiple guards as smooth as silk without breaking a sweat. Difficult to do, but that should be the difference between how Doc moves and fights and the rest of his crew.
From current Hollywood, my cast choices (I'll leave Doc for last):
Johnny: Matthey Gray Grubler (Criminal Minds). You're not going to get the quite walking skeleton as described in the pulps, but you can get tall and thin which Grubler is. He also does smart very well as the genius Dr. Spencer Reed on Criminal Minds. He can rattle off those big words and make it seem like he knows what he's talking about. Maybe a beard to hide his somewhat boyish looks and to give him a professor quality (as well as someone who spends a lot of time in remote places where shaving daily would be a luxury).
Long Tom: Jonathon Young (Sanctuary). When I saw Young playing Nikola Tesla on Sactuary, I thought what a good Long Tom he'd make. Then to discover he has also played Thomas Edison, and it's almost a required casting. He plays smart and arrogant well but not physically imposing. The problem with Long Tom is in reality, he's physically a bit similar to Johnny. Thin people tend to look frail as well as taller. And two remarkably thin actors are going to almost seem interchangeable. A little make-up can get across the pallor aspect and I think the basic different acting styles of Young and Grubler can carry the rest. Johnny will be more introspective, excitable only when something intrigues him or reminds him of history. Long Tom is more mercurial and temperous and excitable whenever he can show off his latest gadgets. Of the group, Long Tom is the one that's always looking to build something new, to apply technology and science to new uses and improve upon the things we already have.
Ham: Simon Baker (The Mentalist): As Patrick Jane on The Mentalist, Simon Baker shows that he can be clever, cuttingly witty, smarmy arrogant and a bit pretentious/metrosexual, all attributes that Ham has. He has that lean waisted and pretty boy looks. Of the Five, he's the only one that should be conventionally called handsome. And, he shows that he wears nice clothes well and looks completely comfortable and at ease in them despite no one else dressing as nicely as he does. Teach him to box some and fence and you've got a perfect Ham.
Monk: Scott Caan (Hawaii 5-0). As with Renny, I think you have go for a baseline with Monk. Now, I happened to work with a guy that in his late 50s/early 60s, he was almost note-perfect for how you'd think Monk would look at that age: gristled and homely face, constantly smiling, barrell chested and large biceps showing that he obviously worked on upper body/arms more than anything else. He was the right age to have been perfect at the time Pal was filming his version. Barring that there's an unknown out there that's the right physical size and age and has a face ala Ron Perlman or Gary Busey, I think Scott is a good choice. A good actor and in good physical shape, he's only 5'6". A few prosthetics, to accentuate the brow and flatten the nose, to bulge out his chest and make his arms hang a bit to the sides and maybe some dentures to give him a rather toothy grin and then raise his voice a bit, but not so much he's talking in falsetto. The idea is to get the spirit of the character but not to veer into caricature. Oh, and dye his hair to a more reddish color. 
Yes, I've left off Pat. Part of that is because Pat's casting really depends on who you get as Doc. I think she would probably be a relative unknown. Also, I'm not sure she's needed for the first movie. One of the problems the movies often make is they want to include everyone at once. If you're doing Sherlock Holmes, then Moriarty has to appear. The Fantastic Four, then Dr. Doom. Give the movies a little room to grow organically and find their voice. Maybe make a reference to Pat, but otherwise leave her out. Ditto for the pets. Johnny Sunlight, I'd leave completely out until the third movie if even then. And, don't try to redo the pulp novels. If you bring Sunlight in, make it a "third" appearance, that they'd faced off in the past. The pulp novels were their thing, the movies something else. Don't try adapting specific pulp novels, create new stories and new villains. The first movie doesn't have to be "Man of Bronze", just because the novels started there. Go back and read it, it's not an origin story. It details where his wealth came from and the death of his father, but Doc and his crew have been around before that novel. They have untold adventures behind them. They are a group of friends who work together. A montage of Doc's upbringing vs the others' in their civilian jobs during the opening credits is really as much an origin as you need.
Anyway those are my thoughts and choices. What's yours?
