There kinda is already an achievement system. When you accomplish something significant in NSMBU the game ask if you want to post what you accomplished to Miiverse. I dont really care for a record showing achievements but i dont see why they cant add it if people are requesting it. As for party chat i think its mandatory to have a cross game chat like feature. You can video call someone or message them while they are playing a game but there should be party chat with more than one person talking at the same time. It would make things less complicated when playing online games.