I was thinking of adding an active piezo pickup to my electric to make it be able to sound like a true acoustic, since piezos mostly just pick up vibrations.
Is this meant to be a question or something? You can buy piezo saddles from Graphtech. Piezo's also need a preamp or they will sound like crap.
Dont expect it to sound like a true acoustic though, they are close, but not the same as a real acoustic guitar.
im adding a radioshack one to my jaguar just to get a odd sound out of it, but its possible

Guitar : Fender CIJ Mustang and a Telecaster
Amp : 76 fender champ
Pedals : BBE green screamer, Big muff, Ibanez LU20 Pedal Tuner, boss loop pedal