Every barge already has a unique role, for defensive mining, high yield mining and solo mining.
Would be a shame if all barges were copies of eachother specialised in a specific type of ore/ice/gas so if I wanted to ice mine and only had one possible ship choice.
Boring.
I really hope CCP continues their current system, but improves on it. Right now the Covetor and Procurer (as well as their respective Exhumers) have a well defined unique role. Maybe they could improve the role of the Retriever and Mack a bit more, as it doesn’t really stand out right now, I never see a reason to undock one of those.
I’ve had an idea before that gives the Retriever a more unique role: solo-drone-mining-barge-retriever-redesign.
My guess is that CCP also wants unique roles for barges, but unrelated to the type of ore/gas/ice they mine as that would remove player choice for their equipment.
Anyone can pick the correct ship for the correct type of mineral:
It takes more skill for players to do a risk assessment on their current circumstances and pick the ship with a matching unique role with the right balance of yield versus survivability that they need in their situation.