Positions like this suggest that promotion to colorbound pieces is a poor design choice.
One could also argue that promoting to the weak, color-bound Ferz enriches Shatranj with an interesting strategic theme: one has to plan Pawn manoeuvres such that you won't promote all your Pawns on the same shade. And definitely do not leave the opponent a defender on the other shade when you are playing for a win. This is already true in orthodox Chess, where unlike Bishops can draw even against a majority of 2 Pawns, despite the fact that these would promote to Queen.
It is true that Shatranj is quite drawish, but I think this is more a consequence of the Ferz being such a weak piece than of its color-binding. I doubt that promoting to Wazir would be much of an improvement.
One could also argue that promoting to the weak, color-bound Ferz enriches Shatranj with an interesting strategic theme: one has to plan Pawn manoeuvres such that you won't promote all your Pawns on the same shade. And definitely do not leave the opponent a defender on the other shade when you are playing for a win. This is already true in orthodox Chess, where unlike Bishops can draw even against a majority of 2 Pawns, despite the fact that these would promote to Queen.
It is true that Shatranj is quite drawish, but I think this is more a consequence of the Ferz being such a weak piece than of its color-binding. I doubt that promoting to Wazir would be much of an improvement.