I think things are going to move to an architecture where there a limited set of nodes in the network manage the currency, and most account owners are light clients of some kind.
If you want this then the Bitcoin block-chain and protocol is the wrong design to achieve it. Services like visa paypal are far better designed for serving many transactions from small clusters. More secure too once you must trust a limited set of nodes to not cheat then protocols which cannot be compromised unless they do offer a better security model.
A fairly pointless comment.
Visa doesn't have any nodes. You can participate in the authorization process in a Visa transaction?