Thanks, Tony, for the Arden reference. I recalled it only vaguely, before your reminder.
Unpretentiously - as appears to have been his style - Arden actually draws rather a concise and perceptive sketch of Welles, warts and all, in that passage. No bull and very "American", in a Hemingwayesque sense. I'd like to find out if there's more where that came from.
The excerpt also reminded me that Arden had worked with Welles previously in radio and that Welles had sought him out for the van Stratten part. There's even an earlier promise made to Arden that parallels one made by Welles to Keith Baxter about one day making a film with him. (In Baxter's case, of course, that film was "Chimes.")
It's interesting that, in neither case was the promisee a big marquee name, making Welles' prophetic vows anything but mere gladhanding on his part. And, while Welles might have offered other such predictions to other performers in his career, by his actions in these two instances it would seem that, given enough time and money, he probably would have made good on all of them. How un-Hollywood!
As I slowly get to know Arden better (not an easy task, under the circumstances) the closer I think I come to understanding Welles' casting choice. Evidently, Welles really wanted an Everyman in the role, a face and name that invoked virtually no audience preconceptions; a blank slate onto which viewers would be free to project their own self-images, by way of identifying with the part. I think he also wanted someone who could convey the character's necessary ingenuousness quite naturally.
And then there's that identifiably American demeanour: determined, adventurous, impetuous, plainspoken, untrusting of old-world airs and posturing yet irrepressibly curious about about who and what engender them. But, in the end and with a Wellesian flourish, somewhat jaded and decidedly un-heroic. A non-intellectual version of his radio incarnation, Harry Lime, which - one on level at least - would explain the character name-change (the other level possibly being that Welles pretty much "owned" the Lime role and didn't want that recognition to conflict with his appearance as Arkadin). He also needed a performer who could "do bland" well enough to punch up the carefully-crafted flamboyance of the many idiosyncratic characters van Stratten was destined to encounter.
Typical of Welles, with Mr. Arkadin he seems to have been intent on clothing his film in the trappings of a familiar genre but only to finesse it towards a far more significant and artful end. Perhaps an actor less capable of, or less content with, a cipher's role might have proven too difficult a clay for Welles to mold to his unconventional endgame. Think Heston in TOE, for example.