It comes down to dual wielding really. I dont mind dual wielding weapons, but the dual wielding spells just seems like a tacked on gimmick to get more out of the dual wield thing. Everyone liked the move from Morrowind to Oblivion in regards to weapons and magic, but now we're going backwards.
You sure only 1 skill? I know in NV and FO3, some perks required 2 skills to fulfill the requirements of being able to get that certain perk. But yeah, with 2h weapons, a person could drop one hand to cast a spell. Someone with a shield + 1h or 2 one handers have no free hands.
Yes, perks will be in trees directly associated with one skill. there will be no general perks, or at least not at level up. Perks will be a lot more mundane than Fallout perks. They will be more akin to the benefits from the different ranks of a skill that were in Oblivion.
I'd rather just have Bethesda focus on more important "stuff" then this to be honest. It's already too late to incorporate this in anyways with the new combat system.
Your referring to spell crafting or my perk idea?