I think you can drill out the center of a small speaker and then remove the paper cover on the coil. If you carefully glue the lens in that spot and align it well, then you can exploit the coil as a linear actuator BUT it will ring. You might have to impress a dc voltage on the coil to keep it somewhat stiff. Then place the coil in a PID loop like a galvo. Now you have to worry about heating the coil. You can make your own by edge winding a coil on the lens and suspending it in a magnetic field or the other way around with a ring magnet but that adds weight. PWM would be a second way to do it and eliminates the dc resistance heating issue.
If you add this to a fixed lens you can get a lot of the capability of the so called liquid lens. You should be able to get with small lens size a khz or two response with 2-3mm travel distance. Not much but enough for subtle effects. Cost should be your time and a few dollars. Guess you could cascade these for some more varied changes. Most of all have fun.