I know this processes. We add almost daily orders to the BO. I am surprised, that you prefer it that way by default. We try as much, to push our customers, to order themself. It saves us time and nerves 😉
We do it the same way: prename.surename@shop-domain.ch. It's true that it makes no sense to set a passwort there. But it's also not a big deal to put something in this field.
You write a lot about many seconds. I don't have such a big delay on my server. Probably your server is also slow. But true I also noticed that this process is not really quick. Not sure if there is any issue with the ajax post request, or if it just takes this time. A video of your process would help to understand, what you really mean.
Yeah that's a bit ugly. We have created an account like store-customers@shopdomain.com. We add all orders there, that don't need any address. The address is then our company address. We use this account mainly for people who buy directly at our house.
Yeah I believe this is worth considering. Especially in the BO, but I have heard, that some shops use such APIs also on FO.
No idea what you mean. A bug report needs to be concret. And it's better to report bugs seperat, not mixing it up in a post, that is about improving/enhancing features.