Of course it's possible... Like you said you'd need seperate volume and tone pots for each... Since generally a passive humbucker uses a 500k pot and an active pickup generally uses a 25k pot.... A passive single coil pickups generally uses a 250k pot.... You would need to install a stereo output jack. Most passive guitars use mono jacks... Beyond that you'd just have to have the wiring diagrammed.... It would be an impractical application but it could work... It depends on what kind of guitar you're looking at putting the pickups in... It's almost not worth ruining an expensive gutiar with an active pickup.... and not worth the trouble spending the cash on a lesser value guitar... but it's all about what you want. It can be done though. You'll just have a whole hell of a lot of wires along with a 9v battery.... I can't imagine that any tech would be thrilled to open up a guitar and find the schematic... haha