Oy indeed. Thank you for your expertise and reportage in this thread.
It seems to me that Into the Woods depends so much on the different styles in which each character sings that an operatic voice in each role would erase that essential distinction. And the fudging of casting verisimilitude common in opera would add another level of disaster.
That said, clearly some opera companies have had good success with Sweeney Todd, Pacific Overtures, and A Little Night Music, all of which seem more closer cousins to opera rep than Company or Into the Woods are.