From my experience, there are much better confirms off of 5A, such as the triple megido combo, double mode change combo, or something more simple like 5AA 22B jC(1) j236CD 214A jB jB jC j236D. These do more damage, use less meter, and put you in a prime spot for oki.
Challenge 27 is still ridiculously strict, so I would write it off as impractical. As far as I know, Aigis doesn't get much from the AoA C ender if she is not in Orgia mode anyway.