Here’s another interesting regret/wish it had happened bit I almost completely forgot.
When Tony Anthony was prepping his film Blindman, Frank Wolff contacted him about playing the main villain, a sort of “you scratch my back and I’ll scratch yours” since Wolff had recommended Anthony for the part of The Stranger in Un Dollaro Tra i Denti. I believe Anthony seriously wanted to cast Wolff for the part, but because Anthony had a falling out with MGM over Allen Klein (who a lot of us know tends to be “bad medicine” more often then good after his debacle as the Beatles last manager) the new producers wanted a big name, and Anthony acquiesced to this, thus ending his friendship with Wolff. Here’s the main info on it from the IMDb
He provided the role of The Stranger to actor Tony Anthony and played the villain in The Stranger’s first movie A Stranger in Town (1967) as a favor for Anthony. The part became Anthony’s most famous role besides his Blindman (1971) and he repeated it three times. Several months before Frank Wolff’s death, according to Anthony himself, Frank Wolff asked him for a similar favor, wanting the role in Blindman (1971), which was finally taken by Ringo Starr. It was kind of deal between them, Anthony would provide him role, because Wolff had done him a favor earlier. But the producers wanted Ringo Starr for the role - Wolff was dropped and had a falling out with Anthony. About one year later Frank Wolff killed himself. There have always been rumors, one reason for the suicide was, he saw his career at an end/thought he couldn’t get the roles he wanted anymore. - IMDb trivia for Frank Wolff
Don’t get me wrong, Ringo Starr is an icon and very versatile in his talents, but I think Frank Wolff would’ve given the film more weight.