sorry correction if I am wrong in opinion, it looks like sending bitcoin or altcoin on the exchange has been implemented, where all users and traders can send their funds or make transfers to other users as long as it's in the same exchange, what's interesting and great about this, if One day, fellow coinbase users do bitcoin transactions using email, I think it is not a difficult job because they have funds deposited in the same wallet, to be exact a coinbase cold wallet, except to transfer bitcoin to an email address that is not a coinbase user maybe it will cool, even though I don't have a coinbase account but there are people who send bitcoin to my email, of course I have to register a coinbase account to claim bitcoin, hopefully I am wrong
Yes. We can already do that inside the exchange and probably just link the email addresses as alias to send the BTC with out fee. I'm not sure how it works but that has been done long time ago without having patent. They would have to become a big network for all crypto users to be able to do that to cheat the miners.
if a bitcoin transaction using a username might be a lot cooler too, I might be able to think positively in this way the transaction would seem to be great if some coinabse users often make small amounts of transactions using bitcoin, so it doesn't pile up on the bitcoin transaction network, but I say before this it still didn't look great if it was done only for coinbase users