Hello,
There is some travelling around in your (preliminary) itinerary, but it's reasonably relaxed compared to what other people on these fora do on their journeys. I think yours is certainly a good starting point.
Should we drop Ribe?
Ribe is a small town of 8k people, so it sticks out compared to the other stops on your trips which are all larger cities (Aarhus 300k, Copenhagen, Hamburg and Berlin measured in millions) - but sounds like that is intentional. It's a nice, historic town and lively in the summer. The cathedral is really its centerpiece, and with a car you can also explore the nature of the Wadden Sea.
Maybe your trip would lack small towns if you drop Ribe? You can find other towns instead of Ribe. But if the above sounds appealing to you, then Ribe is a good option.
Should we skip Aarhus?
I do have a bit of a soft spot for Aarhus (and I think it is well justified). It has a lot of city life to offer, without being suffocatingly large. It feels quite different from Copenhagen. And it has some good museums, and variety of them.
Think 12 days in Denmark would be too much for us, plus it's expensive.
Summer time Denmark has plenty to offer, even for more than 12 days. But it's very human to want to explore beyond the borders, and you do have a point about Denmark not being a cheap country.
Odense was also recommended on your parallel post on the Germany forum, and I can support that recommendation (though Aarhus is still higher on my personal list). There are also many towns worth visiting. When the weather is nice and you want to move at a leisurely pace, there can be something romantic about visiting one of the (many) small islands of Denmark. I'll stop before getting too much off track, my point is just there are many possibilities.
Regarding transportation:
Copenhagen, Aarhus, Ribe, Hamburg and Berlin are all served by trains. So no need for a car to go from city to city, unless you want to get off the beaten path en route. And a car won't do you any good in any of those cities, except Ribe, where it would be essential to access the rural surroundings.
