lucaat Mail-in-a-box works like this.
Yes, but…
As far as I know, Mail-in-a-Box doesn’t rotate the keys either, meaning there are no subsequent changes to the DNS records. Therefore, the only real advantage is that you don’t have to set them up manually, which would be a one-time task with Mail-in-a-Box as well.
However, there are some disadvantages, such as the fact that you only get one authoritative DNS server for your domains by default. This means that either you have to use a secondary nameserver provider or you have to set up and manage any secondary servers yourself. Okay, there’s not much to manage on a secondary nameserver, but still, you should have at least one.
And yes, in practice, you can use the same IP address for both ns1 and ns2 with most TLDs. However, this violates the standard and, more importantly, provides no redundancy. If this one server on which the DNS is running goes down for some reason, all the domains you host on it will no longer work. Therefore, in my opinion, it is better to use a DNS provider. Or, if you absolutely want to host DNS yourself, you should at least run two servers, preferably in two different data centres.