'radically modify' is correct and usable in written English.
You can use it whenever you want to emphasize that something has changed significantly. For example, "The government has decided to radically modify the country's tax code."
TfL confirmed that Wrightbus is to radically modify the rear door.
But the many facets of the dress drawn in delicately shaded blue strokes radically modify the likeness.
For Jorge Campanini, from Bolivia's Documentation and Information Centre (CEDIB), the "scariest thing" about the new law is the power it gives to companies who will now be able to "radically" modify the way "protected areas" are used.
Any attempt to unify these approaches will have to jettison or radically modify at least one of the motivating desiderata.
One thing is for sure: thanks to them, companies not only can design innovative value propositions, but also radically modify the way they operate.
More radically: modify the purely rules-based accounting of the U.S. to include the principles-based accounting used elsewhere in the world.
The present designs for the buildings will no doubt be improved, perhaps radically modified.
Prescription of therapeutic antibodies has radically modified the prognosis of some important diseases.
From 1962 to 1964, he was a member of the Committee on Curriculum Content Planning, whose report radically modified the General Institute requirements for undergraduate education.
To further reduce finfish bycatch, flume tank tests and sea trials were carried out on a radically modified Nordmøre-style grid.
The brothers moved once again in Los Angeles county, to Lynwood, where they created the "Hirohata Merc", a 1951 Mercury owned by a customer, Bob Hirohata, which they radically modified.
