I'd heavily prefer that they just do Chistopher Bonds's play, than Sondheim's musical.
Depp surely can act the hell out of Sweeney, that's not what I'm worried about, but getting an amateur to sing an heavily Operatic role like this is not my idea of a goodtime.
I'd always conceivably like to listen to the soundtrack, and I most definately wouldn't want to listen to Depp's untrained, raspy, thin voice sing Epiphany.
Just maybe he's got a booming, baritone, Brian Stokes Mitchell in him.
....Unlikely.
I like my Sweeneys big voiced and classically trained.
Personally, I think I have too much bloom.