Hi hive,
I regularly make projects with many different parts with varying audio levels.
I also use music, sfx etc in places and I attempt to balance it all as I go.
Although all the tracks and part can have their own volume level, a HUGE help would be a master fader on which to place an audio compressor which can pull it all together.
The project could then be realtime previewed running through the compressor and all levels tweaked accordingly.
Currently the only work around I can see is the massively cumbersome task of having to 'produce' the entire project's audio only then process this with compression abd re-import into the project.
This is a huge pain of you then want to tweak a level and have to redo the entire process again!

Here's hoping!