Feedback Extending Timeline - lot of things are internal, private, ...

To the timeline team;
after I while I gave extending the Timeline another try, and many useful things are still not accessible.

Here's a list from just the last hour of trying to get something to work:

• To make a custom clip that plays audio plus does other things, I had to duplicate the existing AudioTrack as it is not extensible at all (nothing is virtual, most things needed are internal).
  
  
• No way (that I found) to change the PlayableBinding of a track to something else than "AudioPlayableBinding" while still getting audio output; I think this is probably possible but I couldn't get it to work. Would be great to get some guidance on this
  
  
• No way to change the category name on a custom track, Unity namespaces are hardcoded, no attribute for that ("Workaround": if I write "MyCustom.Namespace.WithClasses.UnityEngine.MyTrack" it ends up as "My Track" because the namespace contains "UnityEngine"). Can we please have a category name attribute like everywhere else in Unity
  
  
• No way to change the output icon of a track if it does happen to output to a hardcoded type (e.g. binding is AudioSource > no way to change icon); TrackResourceCache.SetTrackIcon is in private class
  
  
• TrackDrawer is private, can't adjust
  
  
• Undocumented (at least I couldnt find it) behaviour for which types of objects allow creating a Timeline Clip - after crawling through the code it turns out this is based on reflection of public properties

All in all, I still like the timeline system - and I was able to (nearly) achieve what I wanted. But wanted to point out that in terms of extensibility, there are some things that feel weird.
There's probably ways around some of these issues (asmdef hackery, embedding the timeline package, ...) but these all don't feel right.