To keep the price point in the same range (and to keep the accessories part count up, too), instead of a two-pack+BAF, make it one fig (probably a variant of an existing fig) along with a slightly bigger BAF piece?
Also, how about not only BAF sets, but also build-a-vehicle or build-a-diorama sets too. Like battle damaged versions of the TMNTs along with 4 pieces that would build a turtle van or sewer/street diorama, for an example.