There's no way to see the surrounding project from within a Compound Clip. For this reason I would suggest building complex composites as connected clips and only nesting them into Compound Clips when you have the elements lined up with the main storyline as desired.
you can´t scale, blend or apply opacity as a group. That´s why I tend to put them in compounds clips.
You can do all those things in a Secondary Storyline (Cmd+G) - in fact as far as I know, you can do all the things with a secondary storyline that you can with a Primary Storyline.
Select the clips you want to blend, fade or whatever, and press Cmd+4, then adjust in the Inspector.
My point was that you can do these things, and still see the background - which was what you were asking about.