"I am currently considering a Nunatak Skaha Plus with hood and customised internal pockets and a montbell ex light. This would be around 460g for the combo."
This is the combo I use in deepest winter, with a windshell thrown over the top as well. However, I would not usually wear BOTH garments AND a pack, but would probably just wear the Skaha and save wear and tear on the EX light. The Ex-light is sized to fit over the Skaha.
I agree about not counting the hood as extra warmth, as most folks who don't have a hooded jacket would be carrying something else to wear on their head, so warmth wise it should all even out. However it would only be fair to give the hooded jackets a small break for their weight, as they would obviously weigh less without the hood while providing the same torso warmth.