This can be easily built with a 5, 6 or 7 gallon bucket, I invented this maybe a month ago and it works great, if a little leaky but doesn't leak as much with the gamma seal lid. If you don't have the room you can swish it around on a countertop or screw 4 casters to a piece of wood and roll it in place.
Your design has less moving parts so is less likely to fail but does need a large flat floor space to operate it. I like the idea of being able to sit down to do the washing!
My design doesn't require a large floor space, it only makes it convenient. You can sit in a low chair with the bucket in front of you and roll it back and forth in about a 3 foot area, it will probably give more of a back and forth 'washing machine' type action that way as well.
