Hello, all! I feel a little strange chiming in here, as I know very little about 4E. However, in creating an Assassin character recently, I came across a bit of info in the Dragon article that may give a hint of the Wizard's intent on this subject:
IMPLEMENTS
Assassins focus their shadow energy through a ki focus, which is not an object they wield but a reservoir of magical power within themselves. When using a ki focus, an assassin taps into the power of shadow magic and channels it into both implement and weapon attacks.
You can imbue your ki focus with magic as if it were a physical implement. When you have a magic ki focus, you can add its enhancement bonus to the attack rolls and the damage rolls of assassin powers and assassin paragon path powers that have the implement keyword. You can also add its enhancement bonus to the attack rolls and the damage rolls of any weapon attack you make using a weapon with which you’re proficient.
You can also use a weapon with which you’re proficient as an implement. While wielding the weapon as an implement, the characteristics of the weapon you use—proficiency bonus, damage die, and weapon properties (such as defensive or high crit)—are irrelevant to your implement powers.
If you have a magic ki focus and wield a magic weapon, you choose before you use an attack power whether to draw on the magic of your ki focus or to employ the magic of your weapon. Your choice determines which enhancement bonus, critical hit effects, and magic item properties and powers you can apply to attacks with that power. You can’t, for example, use the enhancement bonus of your ki focus and the property of your magic weapon with the same attack power.
I'm not sure whether (or how) it actually bears on the argument but it seems like it does to me. The last paragraph is the one that seems most pertinent.