Honestly I consider Yaiba's events canon (even if is a kind of canon for the NG main series that you can completely doesn't get in consideration so far, something that surely lower its importance), but the point is that this remain anyway a spin-off created in first place from someone that is not Team NINJA, where the main team only cooperated.
This alone make of NGZ a secondary work compared to the rest of NG series, something that IMO doesn't make of it the first choice for TN where to get a character to add in their DoA series, with the exception to not want make specifically a tribute to it (and again, in that case the first to be chosen would be Yaiba).
What would Monday's fighting style even be? I've said this same thing when people were requesting Irene, I don't understand the logic in wanting character X when they've never actually fought before.
It's true that we have never seen Irene to fight hand to hand, but applying a realistic logic the girl should be able to fight being an operative C.I.A agent, and this could be a good way to introduce a such real fighting style in the roster of the series. To this you can add that she already own a part in the new canon, and neither secondary even if in background because support of the ninja acting in first line (but I repeat the same things everytime XD).
From the other side Miss Monday is missing of both the things being a scientist not tied in any way with the DoA plotline (if not for knowing the existence of Ryu and Momiji, that by the way are characters more tied to the NG series). The same Team NINJA stated how they believe that she is not a fighter, and again this doesn't mean that they can't change it (we have just seen a dead character returning alive), but just that at the moment of the conception is never been got in consideration the idea that Monday is a martial artist, so it's logical to think that even now the idea behind the character is that one.
