I played around with rinse aid last night. The theory would be perfect for our needs - breaks surface tension, encourages sheeting, makes water dry faster. All good stuff. It doesn't however have any cleaning power at all and doesn't apppear to break down grease and doesn't mix that well with water - sort of hangs about in a cloud.
Now, rinse aid mixed with Ecover could be on the cards. If I could be bothered.