Todays imagination could be ( normally would be ) tomorrows reality.
Looking at the state of current affiars of South Asia, it could be possible in the coming times.
If Pakistan, India Srilanka could hold a Cricket world cup together then why not a car racing event ( Offroad, formula or anything else ). On such sporting events I dont think the Govts would levy duties and taxes for making an entry.
Why not start with a goodwill car rally starting from Pakistan's
G.T. Road to Calcutta and further ( G.T. Road ) and slowly coming to the point raised by ahad