I was looking at wizard of the spiral tower last night and I think there's something I've been missing. Which other people may have been missing as well. Specifically, having looked again, I can't tell if a fighter->wizard gets to use a longsword as an implement, or whether the implement mastery class feature should be required.
Basically, if I am a fighter->wizard, I don't have the Arcane Implement Mastery feature of a wizard, which allows a wizard to specialize in a particular implement. Corellon's Implement allows me to choose an arcane implement I specialize in, and allows me to use a longsword as though it were that type of implement. They're not explicitly connected, so I can't say for certain that this is a requisite, or if I could use a longsword as a generic implement. If it is a requisite, the paragon path functions for a wizard->fighter, but not the other way around. Given that both powers are weapon-based, it seems tailored to the wizard who takes up the sword, rather than the swordsman who takes up arcane magic. As a fighter type going for wizardry, I would probably want to pick up more wizard powers by paragon multiclassing rather than pick up two more weapon attacks. Which makes humans an ideal race for it.