Would you consider adding an internal video player for video playback? It would make a more complete experience and it removes the need for installing apps like mxplayer or vlc. I believe you already use exoplayer for audio and i think it would be appropriate using it also for videos.
There’s long term plans, but the main advantage of MxPlayer and VLC is that they can support DTS and more codecs that what ExoPlayer could propose without having licensing issues 
This would trigger transcoding when not necessarily needed with other players, and those license are not cheap so can’t fit Yatse pricing model.