Let’s get straight here people.
These aren’t really loose ends, it’s just things you would like to see but simply didn’t get to. If any of those things had been important to move the story along then they would have been there, but they weren’t.
Mike talked about this in the first art book when discussing the flashback to Tarrlok’s childhood, that having a scene like that works when it moves the story along, otherwise it’s just exposition for the sake of it.
I guess it would have been nice to see that, and they probably thought so too. But they had this story in mind and there simply was no room for it, what they showed was enough. Why waste any frames on further exposition when there are other things more important to the story?