Cons: Obsoletes feats which give a +1 feat bonus to attack rolls such as Hellfire Blood.
Yeah, I missed that one. I would say that they should not stack (constant bonuses rarely should), and propose a fix of Hellfire Blood increasing to +2 at level 15 and +3 at level 25. But this leads us down the road of domino-effect fixes...
Alternate proposal: Instead of calling Expertise a feat bonus, just say it doesn't stack with itself. (This could be considered a clarification rather than a change.) Or if you prefer, introduce a new bonus type and call it an "expertise bonus."
-- 77IM