A personal favorite hypothetically remade:
QUICK CHANGE (2010). Written and directed by Jody Hill.
Seth Rogen as Grimm (Bill Murray)

Rogen is the new Bill Murray. No questions asked. Could also pull off some decidedly demented clown makeup for the heist, especially if working with his
Observe and Report director again.
Jason Bateman as Loomis (Randy Quaid)

I remember proposing this in the B Action Thread and being told Danny McBride would be better, but he'd be far too aggressive for the naive looniness of Loomis. If you've seen
Smokin' Aces, Bateman can easily pull off being a loopy wacko. I could also go with Charlie Day, but...
Kaitlin Olson as Phyllis (Geena Davis)

Absolutely killer as Sweet Dee on
It's Always Sunny in Philadelphia, and her angular body type and deadpan timing would make her a perfect successor to Geena Davis.
Tommy Lee Jones as Chief Rotzinger (Jason Robards)

Considering the completely bonkers plot of the film, Jones would fit brilliantly in a parody of his typecasting as determined lawmen in films like
The Fugitive and
No Country for Old Men. Just picture an urbanite Ed Tom Bell if he wandered into one of the more comedic Coen entries.
Jackie Earle Haley as Russ Crane (Kurtwood Smith)
Craig Robinson as Lt. Jameson (Richard Joseph Paul)
Patton Oswalt as Hal Edison (Phil Hartman)
Aziz Ansari as Cab Driver (Tony Shalhoub)
Ken Jeong as Johnny (Stanley Tucci)