I answered to myself no and then yes :-)
So, why going on reimplementing demuxing, audio decoding, audio rendering, subtitles etc...? Raspberry Pi already is a target of the https://github.com/huceke/omxplayer implementation. So, I completely got rid of my implementation and I started leveraging an adaptation of the omxplayer code to make it a library to use in a similar QML component. In a few hours, this was the result:
Unfortunately, I still have no code that I can share and also still I'm experiencing some "interruptions" during the rendering which do no seem to appear in the omxplayer, but if there is anyone wanting to take this road, the result seems really encouraging as you can see! You can start from the code I posted here if you want.