The phrase "altogether impossible for" is correct and usable in written English.
It can be used to express that something is completely unfeasible or cannot be done in a particular context.
Example: "It is altogether impossible for us to meet the deadline given the current circumstances."
Alternatives: "completely unfeasible for" or "entirely impossible for".
This did not seem altogether impossible, for a while.
When this answer was returned, they admired the modesty and temper of Camillus; but they could not tell how to find a messenger to carry the intelligence to the Capitol, or rather, indeed, it seemed altogether impossible for any one to get to the citadel whilst the enemy was in full possession of the city.
The peculiar thing is that I can't find it in my heart of hearts to dislike the man, I think there's good in him and that he can change his bilious complexion – whereas it's altogether impossible for people to change the colour of their skins.
If it were altogether impossible to predict stocks, you might as well fire your broker and hope for better luck in Las Vegas.
Unfortunately for him he had overlooked some pretty fundamental chemistry and come up with an altogether impossible structure.
Looking at the shelves now it didn't seem altogether impossible.
But it was surrounded by a wall which, by reason of its immoderate extent, was very easy to attack and altogether impossible to defend.
It specifies no minimum "floor" for the personal income tax, so the tax ultimately could disappear altogether -- making it nearly impossible for Georgia to pay for high-quality schools and other services without large sales or property tax increases in the future.
We recognized that in "advertising [the repair of Volkswagens, it] would be difficult, if not impossible, for [Church] to avoid altogether the use of the word 'Volkswagen' or its abbreviation 'VW,' which are the normal terms which, to the public at large, signify appellant's cars". Id. at 352.
The Dalai Lama, with some 100,000 followers, has made his home in India since fleeing Lhasa, Tibet's capital, in 1959.Those exiles, and another 6m Tibetans under Chinese rule, make it impossible for the Dalai Lama to quit politics altogether.
Some academics argue the demands outlined by the progressives are impossible for negotiators to meet without scrapping the deal altogether, and argue that Mexico and Canada already have strong environmental and labor protections.
