I barely know the movie, but he played a very flamboyant veteran spy in The Eiger Sanction, so maybe he could've played Nelson Brenner in "Identity Crisis."

His last episode was the next to last episode of Season 5, so that would leave Season 6 & 7, unless he came back for the 80s and 90s episodes. I think he would have been a good fit for the first episode of the new seasons, Columbo Goes to the Guillotine, as Elliot Blake. He might have been good in Murder Under Glass as Paul Gerard playing the food critic as a smarmy extortionist. The final scene of that episode with Falk and Cassidy in the kitchen cooking and the "last supper" would have been a great scene.