How do you tackle old data's immutability? What if someone tries to modify data processed a month ago. What is going to happen?
Do you think Visa/MasterCard speed is possibel with a cryptocurrency?
To be honest, I don't think it's possible at all. Cryptocurrencies are distributed by design. They have to MAINTAIN their data on multiple servers, which means that they have to spend much more time to approve a transaction. They will never be as fast as centralized solutions.