I suppose Sean Connery will always be the "real" James Bond and Nigel Bruce the "real" Dr. Watson to some although many others have successfully played those roles. It's odd how some roles are filled by actors, and we can't imagine anyone else playing them--and, when another actor does happen to play them, the audience sometimes accepts the change and sometimes doesn't. I have a feeling it has to do with the depth of the character--Columbo conveys a reality that we can identify with: he's the guy next door with the usual foibles and ordinary shortcomings, but a heck of a nice guy. The more "unreal" a role (Batman, for example or Superman, for another), we can easily accept other actors playing the part. Just an opinion--I'm thinking out loud here, folks.
Oh yeah Bring in the son, have him be a chip off the old block but in the now.I think it'd be fun(if the show or pilot ever gets made),to have the son call the father every now and then for advice but you never see him,(kinda like the original Columbo's wife), but he's not a slouch.He can break bad, and run the bad guy down if he has to.His weapons would be his mind of course, and ... just toying around.... a Jeet kun do expert?Might be a bad Idea I don't know. Of course most,save the police department,would under estimate him to begin with.That was one of the fun things about Columbo Sr.
So yeah frumpy,disarmingly simple/clever, and a bad ass. Have him put naughty CEO's and Politicians in jail. I would have to say though that no one can take Peter Faulk's place.The son would have to have his own quirks.