Don't bother with a numpad if you have any plans for using it in conjunction with modifier keys, unless you're going to remap it to something innocuous first, like the higher F keys.
Personally I dislike them anyway for social gaming, since it's really annoying to have to move *both* of your hands so far =/ For MMOs that, the modifier+numpad issues, and trouble with reaching modifiers in general (I usually bind modifier combinations with M4 & M5, and even certain left/right click actions).
Really I can't see anything the numpad has over using keys in the left homerow area.... you can easily reach at least as many keys using wasd, esdx, or similar, in addition to being able to reach the modifiers to act like extra layers for certain keys.
It might be interesting if someone released an N/6kro non-transposed keyboard aimed at the gaming market, though. Or better a split ergo using a more natural fan/mitten shape for each hand, and minimal finger movement.