Unfortunatly I haven't had the pleasure to visit MiWuLa so I do not know the limitations with regards to the room. Having visited unique Northlandz in the USA and a number of model railroads in Germany and the USA so that I can compare the experience -- I find myself attracted to the Northlandz way of surrounding the visitor with impressions by making him/her move almost inside a larger than life layout. This is mainly acomplished by the extreme height available (3 floors), by letting the scenery extend to the floor and the ability to allow visitors to move through the layout in many levels. If possible you should consider this -- most layouts in europe are too flat.
The Øresund bridge is a good idea - making the trains go over the visitor's head.
One thing to remember is that in Norway most rail lines are single track -so you should plan for crossing tracks where trains can meet. Normaly only the streches close to the major cities are double track
My idea would be to create a fictional amalgam of a line from Hamburg (there are daily freight trains to Oslo from Maschen) to Copenhagen with two routes - a land line with Storebælt bridge and a Rødby-Puttgarden ferry (moving ferrys). From Copenhagen the line would cross the Øresund bridge, with added interest in the form of lokomotive exchange where appropriate (Denmark use 25000V electricity)
Into Sweden the line splits into two lines - one that is an amalgam of the route Malmø-Gøteborg-Oslo-Bergen (with a branchline to Flåm starting high up going down to sea level) -- double track Malmø-Oslo. The Flåm line would be a focal point, twisting and turning over a small area covering a large height difference. It would end at fjord perhaps resembling the Geirangerfjord with a Stave church
As for Norwegian fjords -- many of them have fish farms anchored.
The other line would be an amalgam of Malmø - Stockholm - Kiruna or Malmø - (Innlandsbanan) - Kiruna (either double or single track - I do not know what is appropriate) and then Kiruna - Narvik (single track with crossing tracks).
Both the Oslo-Bergen and Kiruna - Narvik streches are mountain crossings with a very different scenery from that you find elsewhere in Norway, allowing you to model a winter and a summer crossing.
If you could find a way to model the snow being thrown clear of the track and whirling arround the train.... you could show some of the challenges winter railroding brings in Norway
In Narvik I would have the unloading of a train and loading of an ore carrier as a focal point. Yes, you should really empty the trains of ore, load it into the boat (and secretly send it back to "Malmberget" to be ready to be loaded into another train) Real live loading and unloading (using small cameras to show on TV what is happening inside the loading and unloading sheds) of a unit train....
A fully loaded ore train could pose some challenges for the brakes on the way down from the mountain.
The idea of showing a working mine could be incorporated into a "tunnel" under the Kiruna-Narvik mountain crossing allowing visitors to pass between layout parts. The ore would of course be mined, brought above ground and loaded into the ore waggons
I would probably cheat and make a fake coast route back to Oslo fom Bergen. That way I would be able to maintain a higher train density and create more action for the visitor
Forrest producs would be an interesting focal point. Logs being loaded onto waggons, taken to a sawmill or papermill, converted into paper or plank, loaded into new waggons for transport to a port or over the Øresund bridge and into central and southern Europe