As far my knowledge goes regarding wowza, it supports abr for live streams using transcoder but it's not supported in case of VOD. Now if wowza has an on the fly transcoder, why it is not possible to transcode vod streams and provide abr.
Is there anything that we can do to enable this through wowza. Any custom module will do as well.
To achieve key frame alignment you can use ffmpeg. However, encoding keyframe aligned renditions with ffmpeg has been known to be problematic and unreliable.
However, I did come across a forum contribution that showed a successful approach for generating key frame aligned multi-bitrate rendition for VOD with ffmpeg by doing multiple passes. This was done on Linux and I have not tested. It may not work on other platforms.