Air Traffic Controller - retired.
Airfield Safeguarding Criteria cover a range of issues, including vertical obstacles and frangible items within designated distances of the RW centre-line and end zones. I can't remember any of the numbers now, but essentially the criteria provide a degree of protection for any ac departing the RW pavement, and include an element of "reinforced grass" adjacent to the RW. They are not, however, intended to cover situations where an aircraft substantially departs the operating surfaces.
In a perfect world, given unlimited funds, the area within [pick your own distance] of the RW would be level and unobstructed. How far would you extend? How much of Madrid would you level in the process [or indeed the Bath Road adjacent to Heathrow]?