https://bitcointalk.org/index.php?topic=144471.msg1547843#ms...
Bitcoin's lightning is in many ways the spiritual successor to the original Ripple idea-- a pathfinding network between pairwise relationships, but instead of IOUs, the parties use smart contracts to twiddle funds around in bitcoin payment channels without having to take the updates to the public network.
This fixes the big security weakness of Ripple while preserving the positive scalability properties. Unfortunately it also requires more complexity and limits flexibility somewhat.
Since you as a bank would only need your own fiat currency + XRP, you could materially cut down on additional costs from holding all the other accounts. When it comes time to convert currencies, because Ripple (XRP) transactions settle in seconds, the period you're exposed to market volatility is virtually zero, so you can move in and out of a position in XRP in exchange for whatever other currency you need almost immediately.
With XRP, you replace all those currencies with some amount of XRP. Because all member-banks use XRP when you need to transaction, say GBP to EUR (simple example), you would take your GBP, convert it to XRP, then use that XRP to buy EUR from another bank, that bank then can hold the XRP or chose to immediately convert it back to EUR through other banks. Like I mentioned previously, that whole transaction takes a few seconds, so you're effectively not subject to market volatility that could impact the transaction itself.
But I could more easily just use my GBP to directly buy Euros, with one less exchange rate and one less transaction in the process.
> that whole transaction takes a few seconds
For a bank, that's slow. But even if it wasn't, using an intermediate currency simply takes twice as long for each step.
In this scenario, the transacting bank would need to have (or want) to have GBP for them to sell Euros. While I agree this is a poor example, think of the more obscure conversions. Swedish kronas to South African rands, etc.
Anyway, I won't pretend XRP is a perfect solution. Just seems to me that it solves the edge cases of liquidity while doing so more cost effectively, which in turn benefits the consumer.
No new currency needed.
Though certainly I'd be pleasantly surprised if Raiden still pulls through on their plans at some point.
Speaking as someone who worked on Raiden's core team last year and spent a reasonable part of this year working on a project received a grant from the Raiden Trust [0], the last release is workable, but still requires a lot of elbow grease and knowledge of the protocol to get it running. End users will certainly have a better shot when the light client gets parity to the reference implementation and gets a mainnet release.
In any case, I just wanted to point out that Raiden is a project that is related to what OP asked about and that is still alive and kicking.
[0]: https://hub20.io, a self-hosted payment gateway that integrates with Raiden and abstracts all its complexity from the users and node operators to enable fast and near-instant transactions.