Let's talk about the Kensai

I don't like the Kensai kit. I've never played one, and likely never will. But for some damn reason I feel the urge to mod it. The kit description says it focuses on one weapon above all others... and the game does nothing to make that a real part of play. And, I just happen to have a working mechanism to implement such a thing! So it's only natural, methinks, to do that.

Question becomes, how? What should the kit look like? The "weapon of choice" thing could look like anything - in one kit right now I have it giving an extra 1/2 APR, but it could also give bonuses to thac0, damage, AC, weapons speed, movement speed... really, anything that you can conceive as a weapon equipping effect.

And what about the other weapons? Should they be able to reach GM? Something less?

What about armor? What if kensai could wear armor, but it cancels out their natural combat bonuses?

How about something like:
- Limited to proficiency at level 1, and mastery overall
- Starts with mastery in a weapon of choice, and can reach grandmastery
- +1 to hit per 4 levels
- +1 damage per 4 levels only with the weapon of choice
- 1-point bonus to natural armor class, increasing by 1 every 5 levels up to level 20
- May wear leather armors, but doing so suppresses the bonuses to damage and armor class
- Dual-classing cancels the bonuses to hit and damage

Something like that...