This is a great idea, but I’d like to challenge some of your points.
First, you imply that because Cosmos commits blocks faster than Ethereum, it will be a better fit for micropayments. I don’t think the user (or Medium) will care if their micropayment takes 15 seconds or less. This can be hidden from the user by showing optimistic UI updates, and handling the retry logic automatically.
Second, while I’m sure Basecoin is a great tool for creating tokens, Ethereum has a large and growing ecosystem of similar open source tools for launching tokens, and hundreds of such tokens have already been launched.
Another thing to mention is that the proposed system is actually overly complex. Medium doesn’t need its own public blockchain in order to facilitate micropayments, it can simply do transactions on existing public blockchains like Ethereum or Cosmos.
Alternatively, if Medium prefers not to pay transaction fees on public blockchains for every micropayment (not to mention preserve user privacy for individual transactions), then it can use state channels, a technique which allows instant, private, zero gas cost, transactions on P2P private chains which integrate seamlessly with the public chain.
I would also think that the threat that Medium should be careful of is a third party building a P2P micropayment layer on top of the website, taking advantage of its identity platform and distribution while allowing readers to pay authors directly without a middleman receiving a cut.
If you’re reading this, Ev Williams, then I implore you to consider ConsenSys as a partner in launching your first blockchain products. We are happy to help you navigate the path to profitability in an increasingly decentralized internet.