For the purpose this bomber plays (of getting cruise missiles close enough that they could be fired), there are MUCH LESS EXPENSIVE options.
Think of putting as few as 1 cruise missile on a WWII prop plane from the boneyard, piloted by remote control. The plane and two hundred like it, but only one-tenth of which carry missiles, would swarm an adversary’s air defense system. The attack would be unstoppable.
All the planes would be one-way throwaways. But, none of the infrastructure exposed. We could follow-up with another swarm attack.
Now put the shoe on the other foot. We’re not the only country with the potential to attack a defense system by this technique.
There’s a certain quality to quantity.
Not a bad idea, but don’t you dare use mustangs for that, that would be sacrilege!
The Japanese had the same idea. Only those were manned.