Radagast casting

For years I've been saying that they should have cast James Cosmo as Radagast. I mean no knock against Sylvester McCoy, who certainly delivered on the character they wanted, but imagine Cosmo playing a barrel-chested, bestial, Celtic druid type of a wild-wizard. He could have a weather-stained robe and dirt from his exposure to the earth, but lay off the sham-poo in his hair. Make the man (or, Istari, I suppose) something otherworldly and dangerous!