But if you want a sub-sub-domain? A fourth-level domain? Like new.dev.server.com? At the moment that's very well possible by adding "new.dev" as an A-record to domain server.com. If you decide to automatically add a dot when the body of the text contains a dot, this won't be that easy anymore..
I believe that there are two choices:
1) Leave it as it is. If you really want to do manual DNS editing you'll have to know what you're doing. I think this is the best option.
2) Really create a "newbie"-DNS-editing thingy. Create a wizard-like interface that allows you to choose between "add a subdomain DNS record" and "add a root DNS record" and then guides you through the complete process (and also lets you choose between IP-addresses or hostnames etc.).
I think "we" should stick to option 1 and focus on more important issues