And thats awesome too, I was just wondering where the rules that cover that would be found.
It's the normal multiclassing rules. A Fighter does not have access to Opportune Parry and Riposte or Menancing Swordplay, but when they took levels in Kata Master Monk they would gain it.
Likewise, a Mouser does not have access to Opportune Parry and Riposte or Menancing Swordplay, but when they took levels in Kata Master Monk they would gain it.
When you take an archetype that trades out a class feature, you can never regain it from that class. But if it is gained by another class, the fact that you removed it from one class does not remove it from all classes.
Here's a related observation: the Kata Master's Panache pool wouldn't stack with the Mouser's (Swashbuckler's) Panache Pool because it specifically states that your Panache limited to 1 + CHA bonus. Right? Or since it is from 2 separate sources, you'd add those 2 sources together?
How do the multi-classing rules work for 'pool points' of the same type from multiple sources? i.e. Ninja Ki + Monk Ki or Gunslinger Grit + other Grit?
Grit, luck, and panache represent three different means by which heroes can gain access to the same heroic pool, using it to accomplish fantastic feats. For characters with a mix of grit, luck, and panache, they pool the resources together into a combined pool. (Those who use panache and luck gain twice their Charisma bonus in their pool.) For feats, magic items, and other effects, a panache user can spend and gain luck points in place of grit or panache points, and vice versa.
A luck user does not count as a grit or panache user to satisfy feat prerequisites.