Take a look at
this, and (if you've the patience to read it all) you'll see that Mrs Uncle Phil and I attempted something rather like this.
We took the North Sea route all the way up the west coast of the Netherlands, and it's a lovely route - especially just north of Rotterdam, where small seaside towns alternate with stretches of heathland, dunes and forest. After that, you emerge onto the seadyke and it can be a bit samey. Dutch cyclists' approach seems to be to cycle from bar to bar or cafe to cafe, and you can see why - in places there's not much else to act as a destination.
We also realised we weren't going to get to the northern tip of Jutland in our allotted two weeks, so we took some shortcuts to get into Germany, and, once there, took another shortcut along the Ems-Jade Canal, rather than follow the rather wiggly north German coast. We'd hoped to get a ferry across the Jade Bight, but it was late in the season and only running at commuter times, so we had to make our own way across to the Weser ferry at Sandstedt. We then made a beeline to the Elbe at Gluckstadt. Then we turned north along the North Sea Coast route once again, but once in Denmark, just followed our noses north to Hirtshals. We'd have reached Esbjerg a couple of days sooner, if we'd been heading for that port.
If we went again, we'd probably do the same; the coast route itself becomes rather samey, and there's absolutely no problem with navigation or road-riding away from the cycle route - most roads in that part of the world have excellent cycle routes along side them.
We started off with the Bikeline guides to the coast route. Although they're in German (except for the one describing the Danish part of the route, which is in English), the maps and the indications of where to camp, stay and eat are clear enough. We have almost no German at all, and we managed OK. Once off the coast route, we bought maps locally as we went along.
Our routes plotted on the CrazyGuy pages are accurate, so you could use those if you transferred them. We don't (as yet) do GPSs and gpx files and the like I'm afraid. We have the Bikeline guides sitting idle on our bookshelf, and would be happy to lend them to you if you like; they're not cheap but they're doing no-one any good gathering dust in Yorkshire. PM me if you're interested.
We'd like to do something like this again one day - I'd like to have seem much more of Denmark, including Copenhagen - and we passed through the home of Legoland without the time to spare to stop and visit it! If we went again, we'd probably adopt the same strategy of making a beeline through NL and D to get to DK.
Short answer to your question: if you stick to the North Sea route, I think it'll be a dash to do Hook of Holland to Esbjerg in ten days. But if you're prepared to take some short cuts, it's eminently doable.
Oh yes, and it may be flat, but when it's windy, you wish there were hills. Then at least there'd be some shelter, and some of the time, you'd be going downhill. There's a good reason that Friesland, Saxony and Denmark are full of wind turbines!
