If you download the test version (b321m), it should zero faders in case you close the project before closing Sonar. I want to test it a bit more before I put it as a release, but I think it should be safe.
OSC version is good for the logic development in case there is no real device, it mimic everything you can do and see on your SI24. But as a separate surface it is not user friendly, encoders are too small and there is no labels (channel/parameter names) which are natural for real OSC control (see my OSC Phone preset). But if you have iPad or Android tablet, your computer is connected to local net, there is WLAN and you have $5 to buy TouchDAW, I can upload the preset with TouchOSC layout for it. It is possible to use both in parallel (you can move a fader in TouchDAW, Sonar or SI24 and other will follow, switching to bus/EQ mode in TouchDAW will update the mode of SI24, etc.).
Other possible use case of OSC (but with different OSC preset) is a "build-in display" for your SI-24 which show currently controlled strip names, parameters and values. More useful for live performance controllers, but if your computer monitors do not have space for AZ Display, it can be handy for SI-24 as well.
Let me know if you want extend the preset (other encoder/jog wheel resolution with shift, some button combinations, 8track+4bus mode, full plug-in mode (knobs+faders+buttons), just as possible ideas).