As your mix and level will change per track you do id say the idea of a template primarily for that wouldn’t work.
Interesting take of volume (db) though, comparing flute to trombone. I would add that when we are mixing we are actually relying on perceived volume. As technically a flute can be much louder than a trombone because of simple science. Bass frequencies take much more energy, so in the instance of a trombone and a flute, less air is needed to create high Db of sound pressure for a flute, this is to do with how close the natural waveforms are (closer together for a flute).
Having said that, we feel bass frequencies much more than high because they have a tendency to accumulate, which is where perceived volume takes its stand.
I often refer to attending a concert in a stadium to describe this. When you first enter a concert all you hear is treble, you feel the bass but you’re ears havent climatized to the environment yet (they are in a state of compression). Then eventually we start to hear the low end and the spectrum fills out. It’s the same with mixing. It doesn’t matter much about volume because we feel music too.
This should effect how we mix too. When this is applied to mixing we then understand why frequencies mask others, which then helps us combat it with strategic EQ.
I’ve been lucky enough to see breakdowns of Orchestral mixes that have been mastered by pro engineers and they take this concept to the max, especially in heavy hitting trailer pieces. When I first seen these breakdowns I learnt that everything was a whole lot thinner on its own, especially the strings (my mind was blown). No matter what library we get, we still should be mixing it with EQ at the very least… even with a library such as BBCO which claims to blend well with each other. The issue with full libraries such as this is that yes the samples sound great together because they were recorded at the same time in the same space, but they weren’t strategically carved to sit perfectly with each other.
(back to the mastering thing) Ironically though, it didn’t sound thin at all, and it helped a lot with stereo placement and perceived loudness… yes a flute can be as loud or louder than trombone but this isn’t the point. The point is fitting the instrument into the space effectively, so it slots in and doesn’t mask anything, or get masked itself. Tricky stuff that I for one don’t get right as often as I’d like