The movie in question would have the same script and same shot-for-shot direction... only instead of being made decades ago, it is being made for the first time this year. Try not to approach it from a "remake" point of view.
When thinking of a modern actor to fill a role, consider the description of the character and not the actor who was cast in the original.
I'll start with It's a Mad, Mad, Mad, Mad World.
Harrison Ford as Captain C.G. Culpepper (Spencer Tracey)
Will Ferrel as unlucky dentist Melville Crump (Sid Ceasar) and Reese Witherspoon as his ditzy wife Monica (Edie Adams)
Ray Romano as nervous edible seaweed company owner J. Russell Finch (Milton Berle), Julia Louis-Dreyfus as his exasperated wife Emeline (Dorothy Provine), and Sally Field as his shrill mother-in-law Mrs. Marcus (Ethel Merman)
Billy Crystal and Robin Williams as Vegas-bound gamblers Dingy Bell (Mickey Rooney) and Benjy Benjamin (Buddy Hackett)
Billy Bob Thornton as gullible truck driver Lenny Pike (Jonathan Winters)
Rowan Atkinson as cacti enthusiast Lt. Col. J. Algernon Hawthorne (Terry-Thomas)
Tim Allen as sneaky slickster Otto Meyer (Phil Silvers)
Ben Stiller as psychotic lifeguard Sylvester Marcus (Dick Shawn), Mrs. Marcus' son and Emeline's brother
Kevin Pollack and David Alan Grier as two nosey cabbies (Peter Falk and Eddie "Rochester" Anderson)
Bill Cosby as dying tuna fish factory robber Smiler Grogan (Jimmy Durante)