In reply to Predrag.

Predrag I hear your pain.

I have thought about these issues for years and have brought myself up to a high standard on piano for just this reason. However this does not make me a violinist and the way the bow is held and how it comes down on the string is a lifetime's study, as is the art of sticking a bit of bamboo reed in a mouth. Yet, I see a couple of obstacles that could be surmounted.
Tempo - OK some click tracks are necessary, but in a human performance a stunning performance would be way off exact - for expressive reasons. Its not just we tolerate inaccuracy with our ears, its the way tempi are crafted per PHRASE, each phrase being a collection of two or three different approaches to a string reed bang or pluck. Each instrumentalist has his own tempo track and he plays with it in creative ways, he might give a curving increase of tempo for that eight note scalar run to the octave, where he hits that note loud and with extra attack.... and so forth. I think we could build a way to follow timing in this way.

Secondly articulation and articulation crafting. Each note is a universe in itself. In a real instrument you get to bend and sqeak, with a suite of violin samples you do not, but you could have a feature that enabled you to a] choose the articulation, b] apply artistic effects like accent the attack, shorten the decay. Expression maps are part of the answer, but they are very counterintuitive and techy.

Imagine going into score selecting a phrase on the viola line, you right click, you get to see this pick of a viola and next to it are all the custom settings for this note, you can choose your basic articulation (sample), then you get to play with it in ways that are suitable for that kind of instrument - a stringed instrument. Because its a stringed instrument you get to apply string noise, you get to customise the length and attack of the staccato, you get to play in the vibrato window. Each instrument having its own interface within score. Each note a universe