I think I know how to utilize DLNA and make DS214Play transcoding suitable for Apple TV 3 users.
We should ask iBaa to make simple DLNA client based on PlexConnect code, using same DNS-cheat!
So, NAS will transcode using it's own transcoding feature.
This trick should unfortunately make PLEX APP worthless on NAS due to lack of transcoding support, but the DLNA transcoding itself still should work, I suppose.
Use DS Video instead of Plex. It's a tradeoff between the Apple remote and a tablet to navigate through your library, but if you really need transcoding it's probably your best option in the DS214play.
I already use DS Audio and DS Photo because PlexConnect (or PMS itself ??) sucks for music and photos, I only use Plex for video because I do not need transcoding and the ATV remote (or Harmony remote) is far easier to use, and more "wife/children friendly" than a tablet or smart phone.