Combat Sphere Specialization (Combat)
Your knowledge of one particular combat sphere is without peer.

Prerequisite: 1 or more combat spheres.

Benefit: Select one combat sphere you possess, you treat your base attack bonus as 1 higher for the purposes of its effects, but not for attacks made with talents from that sphere. At 5th level and every 4 levels afterwards, the chosen sphere’s base attack bonus is treated as an additional 1 higher, although the sphere’s effective base attack bonus cannot be higher than your character level.

Special: You may select this feat multiple times, each time selecting a different sphere.
Does this provide any benefit to a full BAB character? I'm unsure if, for example, a level 7 conscript could be treated as level 8 for a single sphere, but NOT level 9; or if since it can't let you have an effective BAB higher than your character level, this does nothing for a full BAB character.

Upon re-reading it, I'm 95% certain it provides no benefit to full BAB characters. It looks like it's meant to make low BAB characters quasi-mid-BAB and mid-BAB characters quasi-full-BAB.