I've always considered the ability to sell Pokemon/items, to Pokemon/item-trading merchants in exchange for money, a helpful and profitable feature — which most MMOs, that I've played, are adoptive of — that can help give a monetary lift to players; I'm assuming this is what is being suggested: an NPC that items are sellable to.
While I believe this may have a place in this MMO as well, down the roads under feasible circumstances, we'll have to consider if PWO is ready for this type of feature yet—there would be an outgrowth of Pokemoney into the economy, from selling items/Pokemon/etc. to it; and some players have cited concerns with an excess amount of Pokemoney circulating in the economy already, thus it should be considered/discussed whether PWO's economy would be ready for another major pokemoney crop.
Moreover to the point of your suggestion, it sounds as if your main problem with the MooMoo Milk is that you simply want it removed from your bagpack. Going off of that supposition, would the discardable option of those items, to remove them from your bagpack, suffice?