Seizing Norway just opens up another front and won't be a way around the British blockade. Its pretty much a non-winner, particularly within the score that the military leaders of the Great Powers saw the war initially expanding within the remaining months of 1914. It would be a move that the Germans may consider in 1916 or 1917, but in the end it would just be troops taken away from another, more important, front.
If suggested to the German General Staff it would have been turned down.
While I agree with David, I'm more willing than he to go into detail to explain why.
Y'see, any diversion of troops to Norway strips them from the important push into France/Belgium. You'll probably need a force about the same size as the OTL BEF (1 division of cavalry and 4-6 of infantry) or larger. You can't strip troops from the armies facing Russia, because they're already small. You can't take them from the armies lunging through Belgium, because they need their men to perform the impossible. So this leaves 6th and 7th Armies.
6th & 7th Armies: 12 Infantry Divisions, 4 Reserve Infantry Divisions, 2 Landwehr Brigades, 3 Cavalry Divisions
They're facing the French 1st and 2nd Armies IOTL: 23 Infantry Divisions, 4 Cavalry Divisions.
So they're outnumbered about 3:2. Deplete them further and there's a chance the French will overrun them. Since the German plan was an unstoppable attack and to finish off France in 6 weeks then crush Russia, there's nae much chance of getting them to divert troops to Norway, which will only be useful in a drawn-out conflict.
In other words, your best hope is to replace the Schlieffen Plan with another plan that takes into account the long term - and
then come up with a compelling reason to seize Norway, worrying Sweden.