A Kensai's Signature Weapon

[eamon]

If it wasn't errata'ed...then why does the FAQ represent it as something obviously different from the CW?

It does not. The Kensai's rule text does not state that you can add a bonus to your bonus. The Kensai can imbue his weapon, and there is a maximum bonus. Unfortunately, there is no text precisely specifying what that maximum bonus means. It might mean the maximum bonus to the bonus, in which case you can take a magic weapon and add a bonus to a bonus and make a better magic weapon, or it might mean the maximum bonus of the weapon - in which case you can still improve a magic weapon, but only if it's currently lower than your maximum.

There are many, many good reasons to believe the Kensai's weapon is limited to a certain bonus, and not that he can add a bonus to a bonus.

Intent: The phrasing of the example strongly suggests the latter. In essence, it says that if you're imbuing your weapon to become a +3 weapon, and it's already +1, you only need to pay the price difference between the +3 and the +1. That's focusing on the bonus you can attain. If the Kensai were able to stack these two bonuses, I would expect the phrasing to suggest that if a kensai increases the weapon's bonus by +3, but the weapon is already magical, he must pay not the +3 price, but the difference between it's current and new bonus.

Intent: The FAQ is an indicator of intent.

Precedents: in general, weapon bonuses don't stack. You don't need to be a 9th level wizard to increase an enhancement bonus by three, you need to be a 9th level wizard to even attain a +3 bonus. Other such bonuses of other classes work similarly; it's the total that is limited not the increment, even though increments are allowed and you only pay the price difference when you do so.

Balance: A +10 weapon by 11th level is seriously overpowering, and would not even stretch a Kensai's wealth at that point.

Rules: notably the table specifies a limit to the bonus, and not to an increase of the bonus. Though it's possible it's some sort of stacking bonus, that's inconsistent with the fact that you need to pay more to increase an already magical weapon with one that's not. Stacking effect don't influence each other's cost like that. True enhancement bonus improving effects such as Bane weapons notably don't cost more just because they start at a higher level.

Consistency: The Kensai's weapon improvement ends at +10. More significantly, it has little stars after +6 and higher saying that a weapon can't actually have a +6 enhancement bonus, but can have other weapon abilities. That limitation would be less specific if it were an increase to enhancement bonus. Finally, the example improves a +1 to a +3 weapon and mentions it only causes the difference in price as an XP cost. But that implies that you need to look to the real factual weapon bonus to at least determine the XP cost. And on that very table line it also mentions the Kensai level you need to have to be able to achieve that bonus - to be able to make a +X weapon you need to be a Kensai level X.

Consistency: Nowhere else in the rules am I aware of stacking weapon bonuses. There are certain exceptional situations in which a weapon bonus is increased (such as bane weapons), but normally, effects simply overlap. Presuming the Kensai's weapon does this special form of stacking without a single line to support it is really odd - not to forget that the XP costs being incremental strongly suggest this is no form of stacking, but of actual improvement of the existing weapon bonus, and if that's the case that the literal limitation on "Weapon Bonus" can hardly be interpreted in any other way.