The old site used to have something to that extent. It was Ok, but I don't think it would be nice to have in the alerter. Too many new comics pop up per day. that thing would be going off like crazy.
I think if they added a new section under the strips and comics it would be cool. Like "New Arrivals: Comic Strips" and "New Arrivals: Comic Book". That way it devides them, and would show you five with a drop down.
Personally I think that would be a great feature, and help a lot of new people build up fans quicker, which would make the site more user friendly for new people.
I'm amazed this doesn't exist already. Okay, so I admit I'm biased having just started running my own comic here but it did strike me immediately as a huge weakness in the DD system.
Yes, a new comic will appear in the "Recently updated" list but it will drop out of that very quickly (possibly even within minutes!) Sites like Belfry and OnlineComics.net both have sections where a new comic will be given prominence for maybe a week or more, allowing it to come to the attention of anyone who might be interested.
In comparison DD's set-up seems explicitly designed to ensure new comics have a hard time getting noticed.