In a word "YES", but in reality the answer is no, virtually anything can be done to a vehicle, but at what expense, and how much work is necessary.

The steering column would require changing for one fitted with an air bag equipped steering wheel, it would require an ECU (electronic control unit) various sensors fitting around the vehicle to trigger the unit, and the necessary wiring and reprogramming of the ECU.
Most ECU's are connected to multiple functions, and control many different functions; so in reality it is not possible to fit an airbag.