Haroon, making simple things complicated won't make your life easier.
What do you have to say about the CAA/FAA safety circulars?
Airbus has introduced operational landing distances containing necessary margins
Boeing has'nt
Say you're flying a long haul for 10 hours after 5 hours upon entering some FIR ATC tells you to divert to the airdrome X, with LDA 9000 ft,
What if they tell you to land at airdrome X, with LDA
7100 ft.
If your actual landing distance as per Boeing QRH (unfactored) is
7000 ft, can you apply it and land safely?