Would it be possible to use an Induction Heater on the Shaft, assuming you cold lay your hands on one of course?
With the swingarm removed, you can get a pry bar and a bloody great hammer on it, better weapons of choice...... A turbotorch or similar will heat it if really needed, but I'd wager that some leverage inside the spline knuckle onto the gearbox output shaft end combined with a good whack will see it undone.