You are allowed to have up to two Wallys on an account with a Hopper, but they would both have to be purchased. Also, they do not integrate with the Hopper. You would need to add your own external hard drives to the Wallys in order to have DVR functionality on them. So, there would be a little bit of an expense up-front to switch. However, it would resolve the pixilation issue for those two rooms. Perhaps the other two Joeys could be replaced with Fire sticks so you could stream using the Dish Anywhere app instead of using a Joey. In that case, it would actually lower your monthly bill, by eliminating those receiver fees, in addition to saving you money by not purchasing the local channels.
Great idea on the Firestick. I do own 3 and wasn't aware I could add Dish Anywhere app.