I'm considering the option of taking a weapon kata on my character, but also still training in dagger normally. The issue I foresee, however, comes when calculating the number of kata hits (= normal MA hits + (Max weapon hits vs. AT) - (Max MA hits vs. AT)). This is because dagger (or knife, the recommended kata of at least 50 OB) naturally does less max damage than martial arts strikes, which would result in a negative modifier. This is also true for other weapons, such as main gauche, rapier, and short sword.
How should this situation be resolved? My GM suggested using the absolute value of the calculation, but that seems to completely upend the point of a weapon kata, other than simply to add more crits. The examples in the books, morning star (ALCL p.29) and war hammer (RMC5 p.11) sidestep this issue by using weapons that give more max damage than MA strikes.