The phrase "as unimaginable" is correct and usable in written English.
It can be used to describe something that is difficult or impossible to conceive or comprehend.
Example: "The scale of the universe is as unimaginable as the depths of the human experience."
Alternatives: "beyond comprehension" or "inconceivable."
But it is not quite as unimaginable as it appeared last Thursday.
This is still seen as a highly unlikely outcome, although it is not as unimaginable as it once was.
Arizona was also the last state to join the interstate highway system, a refusal that now seems as unimaginable as the fight over Medicaid will one day become.
Remarkable as it is, the accomplishment is not as unimaginable as it would have been 20 years ago, when players developed more slowly.
For Ms. Fragnoli, going on a date at the time was as unimaginable as drinking a martini when you have a hangover.
To Mr. Lyon's fans, his move to the capital of country music is as unimaginable as the New York Yankees relocating to the Meadowlands.
As the men confront the unimaginable, as well as a deep communal bond, we witness the horrors of totalitarianism and anti-Semitism.
To a degree unimaginable as recently as 2004 — when Karl Rove and George W. Bush ran a national campaign exploiting fear of gay people — there is now little political advantage to spewing homophobia.
Ms. Liu's experience, all but unimaginable as recently as two or three years ago, is increasingly common in China, where a once totalitarian system is facing growing pressure from a population that is awakening to the power of independent organization.
Perhaps one day we'll witness the transmutation of social networking into an as-yet-unimaginable kind of art — 140-character sonnets or mash-ups of media we haven't heard or seen yet.
And here I was, their latest signing, arriving nearly an hour late and causing a customer to scream at the top of her voice as she witnessed what she described as the "unimaginable horror" of my bloodied white shirt sleeve.
