They lower keys all the time in musical theater.
I remember when "Live From Lincoln Center" broadcast "Little Night Music" with Regina Resnik as Madame Armfeldt. In an interview, she commented on how all the reviewers commented on her "whiskey baritone" with "Liasons."
She wondered that maybe next time they could raise the key of her songs, as you would wonder if you could get the Pope to perform your gay marriage. And I remember thinking that they lower keys all the time in musical theater, it's just in opera that they rarely do...
"A coherent existance after so many years of muddle" - Desiree' Armfelt, A Little Night Music
"Life keeps happening everyday, Say Yes" - 70, Girls, 70
"Life is what you do while you're waiting to die" - Zorba