Dolby Vision

Unless I am missing something, why couldn’t one just remux the stream from the mp4, change the container to mkv and re-add the original hd audio stream ?

Just an aside–
I have a vizio p series (2018 model) and its native plex app does not direct play the LG dolby vision demo as Dolby Vision. It doesn’t even display the demo as HDR10, it just shows it as normal (SDR). anyways, same issue with other DV content through plex. I was excited that other users have reported that their LG tvs are able to play DV through plex, but so far with my vizio the only way I’m able to display DV is through streaming apps like amazon prime (jack reacher). I wish the native plex app on my vizio recognized DV tracks and played them properly as apparently the LG plex app does. Any ideas to try to make this happen?