Conventional mixing isn't the main thing with classical music. It's more about musical arrangements and articulations than the mixing techniques usually discussed here. As mixers, our job is really about letting the instruments speak for themselves.
Long before digital audio or even electronic audio, composers and conductors were the mix engineers. Panning and levels were set by where each instrument was physically located on the stage, with the conductor serving the role that automation plays in modern productions.
In particular, Beethoven probably contributed the most in this regard, and his stage setup has not changed much since. That's why most orchestral libraries follow the classical arrangement of instruments in the panorama, making them very easy to mix.
When there was no "sweetening" - no effects, no post-production automation - it was up to the players and the conductor to add interest and dynamics. When composing electronic music in a classical vein, we usually follow the same philosophy, relying on different articulations to keep it interesting.
I am not an EWQLSO user, but every sample library offers multiple articulations and some way to switch between them, usually using keyswitches, keys that don't play a note but rather enable a different sample set. This allows a violin, for example, to quickly switch between legato and staccato. This may be the added touch of realism you're looking for.