Might not be so bad considering that all the plastic is on opposite side of fiberglass board. When desoldering connectors or smd chips, it's often hard to avoid directly blowing hot air at the plastic bits. That's not the case here. Having dots grouped in rows of 7 makes things a bit more challenging. As it means heating up larger area and increase chance of them getting stuck even when all the solder is molten.

But the theory would have to be tested and there aren't many people with so much flipdot panels that desoldering is a major concern. And ones who have few some don't want to risk it. So bulk processing techniques are likely underexplored.