The phrase "all so extensive" is correct and usable in written English.
It can be used to emphasize the vastness or comprehensiveness of something, often in a descriptive context.
Example: "The resources available for this project are all so extensive that we can cover every aspect thoroughly."
Alternatives: "entirely extensive" or "very extensive".
On the East Coast, the New York Tribune wrote of the doubters, "They are certain that no six-year-old could have written these chronicles, so rich in classic lore, so well sustained in narrative interest, and, above all, so extensive that the mere physical labor involved would be worthy of a highly systematized author of bestsellers".
The seizure of Jewish assets in wartime France was so extensive that all Jews, whether the richest bankers or the poorest tailors, were touched by it.
The list of such potential subjects of idolatrous worship, which al-Wahhab condemned as idolatry, was so extensive that almost all Muslims were at risk of falling under his definition of "unbelievers".
The series includes eleven amputations of one lower extremity; all were in adults, with infection so extensive that excision was considered impractical, as the patient would be left with a foot and ankle which were worthless from a functional standpoint.
In the eyes of Lisa Thomas, the needs of the 15th Ward are so extensive it is difficult to list them all.
Marine transgression was so extensive that in North America, for example, a seaway spread all the way from the Arctic to the Gulf of Mexico in the Cretaceous Period.
Soane's collection is so extensive that it is impossible for all of it to be on display at once.
Some surgeons obtain permission to remove the limb, before attempting the operation, in case the disease is found so extensive as to make the removal of all portions impracticable.
Beware of ending up with a list of references so extensive that nobody will believe you have read all of them!
The involvement of ephrin ligands and ephrin receptors in vascular development is already so extensive that it is not feasible to review all the studies here.
The judge's order sanctioning the initial arrests ran to 611 pages, and was based on a collection of phone-tap recordings so extensive that even a fortnight later the prosecution has not had time to fully study them all.
