Pardon the disorganized thoughts here:
I'll tell ya what I did for my template and Synchron Stage MIRpro settings...
I imported a couple of modern classical recordings (not film scores, because they "cheat" the levels on things like the harps, celeste, string shorts, etc) and then did mockups of those excerpts. I think one was Nimrod by Elgar, Beethoven 3rd opening, some tutti chords from Mahler 5, stuff like that...
I made sure that the velocity cross fade of the instruments were at their proper levels, not all jacked to 127 just so I could hear them. But where the manuals said the layers were marked.
THEN I went to the faders in VEPro and matched them to the recordings.
One thing that will help is making sure you find the honky resonances in the MIRpro EQ at the bottom of the instrument profile on the right hand side.
Then there is balancing the instruments in MIR with the Synchronized or Synchron libraries. I used those as a guide as well for balance, usually starting with the "Classic Surr to Stereo" preset and then matching the VI libraries to that (so long as it was also close to those modern orchestra recordings).
I can't remember where the FF chords landed on my stereo bus, but I'm sure it was in that -6 range. I almost always end up automating the stereo bus fader on super soft stuff (like that Elgar variation). And in my experience, the lower levels are even with the loud among the instruments.
Then there is the aspect of color and tone intensity.
Watching rehearsals of great conductors, they stop the string section all the time when they lose the intensity on soft passages. For this, I lower the expression, but even if marked pp, I'm using a mf velocity crossfade level. That shouldn't effect the levels except if you want to bring out a group, like the horns. Instead of automating each expression fader (4, 6, 8?!) I just grab the horn bus and ride it a little bit to help with swells or whatever.
So yeah... faders are always in flux, and those natural volume levels are a great place to start, but I think they can be tailored to your personal programming tendencies.
OH! important thing... also be prepared for some CC24 filter automation. Sometimes you need loud trumpet or horn, but not so brassy.. a nice "ohhh" tone. Use the filter. Also, with high strings/woodwinds all up in the stratosphere, use the filter a bit on the strings and suddenly you'll get a better balance of woodwinds (not to mention not letting your strings get all icy). So maybe as you are checking the mf balance of the orchestra in the upper range, before adjusting the fader, try the filter.
Adhere to orchestration principles. If you have 3 flutes on middle C, playing as loud as they can, and a cello melody in tenor clef with some french horn chords gluing things together, those flutes should not stick out. If they do, your flutes are probably too loud across the board.