I know I have asked for this before, but I think this may be a closer reality now.
Bookends now has an attachment viewer window, and the latest release of Bookends can show Mellel files without actually opening Mellel. And the text can be copied and pasted. This lead me to hoping that DT can do the same.
Now, the view isn’t a perfect 1 to 1, much of the style is not retained in the Bookends view, but it is still really great. I’m hoping DT can look into doing this as well. I don’t particularly care about editing Mellel files, but having them included in searches, and being able to view them in DT is a top on my DT wishlist.