Augment Form

Type of Feat: General
Prerequisite: Spell Focus Transmutation
Use: Selected (mode)

The character becomes skilled with spells and abilities that allow him to assume another form. For the duration, the character’s base attack bonus becomes medium (unless its already higher) but cannot exceed the character’s HD. As example, a 10 Wizard 10 Eldritch Knight will have 17 BAB.

Affected Spells and Abilities: Polymorph, Shapechange.
Has been added to the feat list of Archmage, Hierophant and many other PrCs.
Contrary the feat description your base attack bonus does not become medium for your level. Nor does it matter if your new BAB would become greater than medium BAB of a character of your level. Instead, this feat actually just treats your low BAB classes as if they were medium BAB classes for the purposes of calculating your new BAB while shape shifted.