As someone who makes cold brew every day, this is one of the two approaches I've considered to speed things up, the other being one of those magnetic stirrers they have in chemistry lab. However, after careful consideration, the real low-hanging-fruit here is the time it takes to grind the coffee, load it, fill the water, clean the filter, and rinse the jar. If a cold brew machine could automate these steps (like some hot coffee machines do) you wouldn't care about making a cup in 3 minutes because you'd always have an automatic jar ready for you from 24 hours ago.