Totally random thought; maybe Kurosawa gets called in for a brief consultation/visit at some point during the filming of Magnificent Seven. Spending a couple days on the set could not only give him the inspiration to make a Western of his own, but might also give him a bit more familiarity with how American film-making works, which might let him avoid/lessen some of his early stumbles.
*shrugs* that's definately a possibility. Would make for a good POD.