MASN would risk all their carriage agreements with Cable/Sat/Dish if they stood one up though. Those contracts are worth far more than they could ever re-coup in selling MASN standalone.
How does this resolve itself? It's not just a MASN problem. Are all these RSNs forced to just ride out the dying cable model and they'll lose out on a generation of fans? Does MLB step in and tell everyone to wise up and take a short term hit for long term benefit?
RSN's command the fees they get from cable/satellite by offering them exclusivity. If they break from that model and start offering consumers another reason to cut the cord the cable/satellite companies aren't going to accept their current fee structure or sit around and watch their business continuing to slide into oblivion.