Human milk banks exist, as the concept of wet nurses, so sharing milk is not a novelty concept.

Humans also retain the capability to digest milk throughout their entire lives (yes, exceptions apply), so the problem of biological use is already solved as well.

The last barrier may be on the level of actualling producing it, perhaps?

Unlike animals, humans can actively consent on having their milk harvested for consumption by others.

So, the only hurdle to really solve is perhaps the resistance or taboo of human milk being like any other milk, if not even fairer.