Interesting idea, but I think if the idea is just to reduce electrical noise, the best thing to do is to treat the cause instead of the symptom. By that I mean instead of trying to cover up the noise by perfectly replicating it with the phase reversed through software, you would be better off eliminating noise before it gets to the signal. My favorite design cliche is K.I.S.S. (keep it simple stupid). People have been eliminating noise from car stereos for many years by adding filters, fixing grounds, separating power and signal, etc. I think that's your best bet.
Don't get me wrong. I'd love to see that work if you know how. I think it's more complicated than recording the noise, though, since most electrical noises I've experienced in car stereos go up and down in pitch with RPM. Probably would have to be generated in real time. It would take somebody much smarter than me to do that.