Well, if this were a few years ago, Bruce Campbell.
A couple of actors who would give interesting spins on Flint would be Johnny Depp, and Seth Rogen (he losts ALOT of weight and is not too old). Both actors don't take themselves too seriously a la James Coburn and have great timing on delivering funny dialogue.
I'm not a big Johnny Depp fan but it might be intresting spin on the Flint movies. Just don't know if the movie would work now. Just how many people would get the Jokes of an Over Sex Super Spy since they killed that aspect of James Bond with the Greg films.
There is more Gravy about you then the Grave. Scrooge.
It just can't be done. The spy craze (and the Flint parodies thereof) were too much of their time. Any remake would have to be tongue-in-cheek with regard to the 60's . . . . the way Down with Love (2003, Ewan McGregor & Renée Zellweger) was with respect to the Doris Day/Rock Hudson romances, and look how forgettable that movie was.
Yeah, I agree that it could not be done today. The closest thing to this was the Austin Powers and people seemed to like that because of it's silliness. I couldn't stand it. I am not sure I could watch the Flint movies at this point they would be so dated, but I remember thinking they were so cool as a kid. Also, technology today has gotten so bizarre it would be hard to think of techno-gadgets that would make the Flint character interesting.
It would seem like a rehash of Austin Powers, however . . . they did Spy a year or two ago with Melissa McCarthy and Jason Statham. It was pretty funny. That knocks out Jason Statham as the lead in a new Flint franchise, though. I would vote for Daniel Craig.