Jack Iverson and Johnny Gleeson would be delighted with that idea.Would rather they learn the carrom ball instead. Far less likely to chuck it, and presumably less stress through the joints.
I find it hard to believe that bowlers like Murali, Saqlain, Ajmal haven't mastered the non-doosra skills of bowling off-spin.There is also the ball that 'Drifts' away from the right-hand batsman before spinning back. 'Drift' has been used to good effect by all the great Off Spinners.
So basically the Doosra is used by those Off-Spinners who haven't mastered, or can't be bothered mastering, the usual skills of the Off-Spin bowler.