WDTV not streaming files with subtitles

[Zathor]

Since the change of the WDTV renderer ~7 months ago to the mediainfo format most of my MKV files will not be streamed anymore. Instead transcoding is used which leads to a problem as I cannot select the subtitles directly anymore. If I set StreamExtensions = mkv this problem is solved. Log is attached for original renderer config without streaming.

I assume the problem is that files with subtitles will now be transcoded as in the renderer subtitles cannot be selected to be streamed like video/audio/container formats. Is it possible to set the supported subtitle formats (PGS, SRT, ...) to be streamed without using the StreamExtensions = mkv hack?