Well, though I am in the minority (as in, votes = 1), I think Val Emmich has Ozzy's facial features big time from his Sabbath years. He's a singer/song-writer, and he's an actor. http://bluhammock.com/asset/val_9335_snowhat1APPROVED300dpi.jpg
To me, he looks tremendously like Ozzy did some 35 years ago.
Tobey Maguire (ya have to imagine the long hair for both of these guys, and Maguire doesn't have a dead-ringer on his lips like Emmich does):
http://blog.luxuryproperty.com/wp-content/uploads/image/celebs/Tobey_MaguireSpider-Man_3.jpg
Daniel Day-Lewis looks a bit like Bill Ward to me.
http://crfranke.files.wordpress.com/2009/07/daniel-day-lewis_l.jpg
But the actor you mention would work as the younger Ward.
Joaquin Phoenix would be worthy of Ward too:
http://www.ankegroener.de/anke1/Bilder/joaquin_phoenix.jpg
For Geezer, one guy I think who would work well is Ralph Fiennes. But damn Geezer had a helluva honker in the days (LOL), the thing is that they have similar eyes and facial features (excepting the schnozoo).
http://www.ankegroener.de/anke1/Bilder/ralph_fiennes.jpg
or Christian Bale: http://www.thecinemasource.com/moviesdb/images/Christian_Bale%20-%201%20-%20Rescue_Dawn.jpg
or Daniel Day-Lewis: http://harmanonearth.files.wordpress.com/2008/01/butcher.jpg
And for Tony Iommi, Matthew McFadyne could carry things off, if you put the big hairy-@ss moustache on him. LOL.
The I AM OZZY books is great, and would make a great movie! I heard rumors once that hollywood wanted to do a Ozzy/Sabbath movie. There is no excuse now. There is a great script right in their hands with the Ozzy book. So, who could do it justice? From the actors to the director, etc. The only person I can think off the top of my head is who could play Bill Ward, and that is James DeBello (he played "Trip" in the film Detroit Rock City). I think it would work if he was given a mustache, etc. But I don't know if he could do it justice.
I'd really like to hear some serious opinions here. Who do you think could pull it off? I'm not that familiar with younger actors. Any ideas? Cast the movie, I'd like to hear it!