This should be an easy add on to the Hopper in settings to sync A/V with at least one joey. Since the Hopper is the streaming server for the Joeys it has no A/V delay and all joeys will have a streaming delay of 1 to 10 seconds depending on distance and splitters used from a Hopper. A fix would be to add an adjustable A/V delay of 1 to 10 seconds to the Hoppers live A/V outputs in setting. This would allow you to adjust the A/V delay so the Hoppers live AV outputs can sync with at least one Joeys A/V outputs. It would sync best with one Joey with the right delay setting. But If you use more Joeys that are about the same distances and used the same number of splitter's from the Hopper they should still sync well enough with the right delay setting.
My hopper 3 install is 3 days old. Pretty sure I'll be calling Tuesday to switch it back to my old system. Unsynchronized televisions are an unacceptable situation. So you're going to tell me the televisions in my local drinking hole can't use Dish? I think not.