Uhm, city list? Yeah,
here.
Actually, Harald would be a better leader for ferocious Vikings I would like to design. Cnut belongs to the nightfall of viking era, where seafaring, bloodthirsty norsemen settled down. On the other hand, Cnut is quite an amazing material for civ leader (achievements). He is representing the peak of Vikings' might.
I would truely like Vikings to be terryfying and have their time-window at early medieval (like Shaka with Impis). I would go with Berserker replacing Swordsman, trait once more would be based on Medieval Era. Current Denmark isn't bad, however it is quite bland.
Who knows, maybe somebody; Hiram; would make late medieval Denmark and unleash Vikings fury. I would
help. I think adding <Playable>false tag to current Denmark and making new denmark civ (remember of unique tags) should effectively remove any issues with other mods interferring with Denmark.
In this case, I would go with Harald (my leaderscreen would be an option for people without dlc).
25%, still not bad.
I agree that North Sea Empire under Cnut the Great could be a next civ. However, I would probably leave it to other modders once I had my bloodthirsty Berserkers. That unit in Civ III was hilarious.
@The Malacca Sultanate - sorry, they do not seem to have any scientific (engineering aspect isn't amusing as well) achievements. I would like to carefully pick this civ (well, Germany could do; America would also fit). What is a twist of fate, mentioned Mughals might do. Actually, I have modded policies so that all branches are available at start (see, I have never made any civ bonus based on Social Policy system for the reason; modding Policies was on my horizon for a long time).
What is more, your reasoning about Longships is valid. Runestones would be nice (Stonehenge can be made as Improvement?).