Some people have put together acoustic simulation presets that are useful in a live situation, but I've never heard one that I would call convincing.
I think you'd be better off trying to tone-match an acoustic recording instead of a piezo pickup. Piezos don't accurately capture the sound of an acoustic guitar, either. Acoustic tone matches are way better than nothing, but there are things going on with an acoustic tone that a magnetic pickup doesn't even respond to.