Adapted works of CC-BY licensed works are not restricted to the same license. You may use any license for the adapted work, as long as proper attribution is preserved.
However, you are using mechanical transformations to modify the original work. As these transformations lack any element of creativity, you have no copyright for “your” modifications and therefore no right to issue a copyright license of your own for this adapted content. (However, the threshold of originality is jurisdiction-dependent.)
In particular, section 2(a)(4) allows technical modifications of the work for format shifting, and states that “For purposes of this Public License, simply making modifications authorized by this Section 2(a)(4) never produces Adapted Material.” Purely presentational changes definitively fall under this section.
So while you may not be able to issue your own license for the transformed works, you may license a service or a software to perform this transformation (but not the transformed works themselves), and you may hold database rights to a collection of these works (but not to the individual works).