Very interesting work. I really liked the melody you opened with. Very innovative sounding with a fun rhythm, would have been cool if you threw some counterpoint in there, to keep it a bit more fresh. The second section seemed almost minimalist and had some really cool textures. You were smart to keep the intervals wide between the bass and viola here. Your atonal sections were pretty well written too. The Vivace section got on my nerves a bit though, seemed a bit too redundant without serving any real purpose. It just dragged out a bit too long for my taste. I felt the same way about the Maestoso section, and the transition (or should I say lack there of) at the end where you returned to the first section didn't really seem to fit. You should also be a bit more conscious of your dynamic markings. Remember all dynamics are relative. My rule with dynamics is to keep the Ps and Fs balanced, for instance I would never put in a fortississimo if I did not have AT LEAST a pianissimo. If you really want a section to come out with more volume, I would recommend using more descriptive texts to illustrate that to the performers (things like con brio, dolente, dolce, ect.). It comes out a bit more tastefully to the performers and the audience. Also, NEVER EVER EVER use double sharps or double flats, there is ALWAYS another way to write them. I can understand from a compositional standpoint why you would use them, but it will waste the precious time that a performer/ensemble will need in order to prepare a piece. I would check some of these tessituras, too i think that high D may be a bit too high even for a retuned viola.
ALL of that being said, this is a cool piece. Its kind of like a sampler of all of the twentieth century techniques and movements, and a lot of the extra notes you put in there (like the retuning of the violin, ect.) for the performers are really interesting ideas. You really seem to know how to express what you want to hear in the music in written form, which is an incredibly powerful tool for a composer. Great work, keep it up!