Great video, I don't understand some technical aspects very well, so this might be a dumb question.
1. Exchanges are already running their own trading systems that only reference the bitcoin network when bitcoin are deposited or withdrawn from the exchange. So exchanges could in theory run their own separate blockchain which would be more transparent and verifiable while your funds are in the exchange system and only reference bitcoin when you withdraw or deposit bitcoin from that exchange/possibly future blockchain. Is this kind of how off-chain stuff could work?
As to why new dacs might attach to Ethereum...
2. Is ethereum's USP maybe that it's being done with Goldman Sachs involvement?
What if GS make Ethereum the only legal 'base' crypto and Goldman Sachs also give it the only legal Western crypto to fiat gateway/exchanges.
So the only legal Western exchanges are run by them and you can only trade fiat in and out of Ethereum. (They make laws so that the only Crypto Western online retailers can legally accept is Ethereum as well.)
Then lots would tag onto ethereum because whatever virtual assets/dacs they create will have to be traded out into ethereum if people want to exchange them for fiat or buy stuff from large online businesses.
2> I believe the only people who are, at this moment, having problems getting fiat in and out of the system are people outside of (western) Europe. Germany for example has bitcoin.de, an exchange ran by Fidor Bank, all perfectly legal. I just sold 100EUR worth of BTC to a webshop here in the Netherlands. Fill in bank account; send BTC; money is on my account within the hour. Buying goes just as easily and instantly through my online banking account. All perfectly legal.
The issues, and dangers, seem to lie in the USA's antiquated banking system and its reliance on Credit Card companies. So indeed you should keep a sharp eye on a private party attempting to hijack the gateway system. People are worried about BTC becoming centralized, where they should perhaps worry about they attempts at erecting a wall surrounding the ecosystem. Where you either buy from a corporate gateway or buy from the back of a trunk.