Hey Hey Hey,, Whos says that they dont work when replaced with new ones ??
I like your approach,, yes plz go on with the replacement of airbags with new ones..
If you dont place new airbags and just cover the openings with a new dashboard and steering flap. You can be responsible for some one's fatality, When you sell your car the new owner would not know that the car has no airbags and he or his family might get severely injured in a collision (Allah na Karay aisa ho) , Think of it for a few seconds, I am sure your inner human would never let you do such thing..
My friend got his Accord's airbags deployed.. He covered them with new flaps of steering and dashboard while he kept the car , and when after few years he decided to sell it off , he bough the new airbags and got them fitted and beared a high cost as well, His stance was that I dont want to be responsible for any1s death or injury just because i saved a few bucks and never got the airbags re-installed.