Almost any reaction can be selective, sort of. If you are asking about doing this in the lab, I'd give it a try. Just limit the cyanide being used. Then it will become a question of isolation.
I don't necessarily see how protection would be better unless you come by the keto-aldehyde by a route that had one group protected or masked in some manner. Protect, isolate, make cyanohydrin, additional chemistry(?), deprotection doesn't necessarily look like an improvement in isolating your desired product.