Great businesses that aren't being built yet?
Nice list. In particular, I think consolidation of payments infrastructure and the anonymous credit card ideas are great though both are some what opposed to each other!
 Merchant acquiring doesn’t need to exist anymore... Just look at the amount of small shops who refuse to accept AMEX or small card payments - they are price sensitive to acquiring fees and some of the savings could be offered to customers an incentives. As you note, network effect is the hard part but I’m sure there’s a way.
On anonymous payments, I think a credit or debit card like thing that offered anonymity online when buying things would be quite attractive. I would use it. In the EU, you could implement it with open banking and there are various services which already provide virtual card numbers. Problem would be dealing with all the payments regulations.