Wouldn't modernizing things here and there not also mean that at some point the entire airplane has to go trough the approval processes again because it is now

Wouldn't modernizing things here and there not also mean that at some point the entire airplane has to go trough the approval processes again because it is now no longer considered a 747 which in turn also means all personnel need to be certified for the new type? I once heard, that is the reason why many airplanes still have a "no smoking" light switch in the cockpit although it does not do anything anymore.