funny you bring this up...I was brainstorming last night with a buddy...we both get in trouble when we think! Water pressure powered sausage stuffer...which is pretty much a piston arrangement powered by city water pressure. Later on I begin to wonder IF one could be adapted to crush grapes and I think it could. Sort of opposite from what you want to do...well OK, it's completely different!
Bet your buckets would be easier to clean up afterwards.