I suspect you wont like the answer: on the other hand it is a "self inflicted" loss.
There is a chink of light....in portugal at least, they are looking at a bilateral agreement to avoid the quarantine. Maybe that will result in similar agreements.
It is so impractical that I do not think it will happen for long. It will kill not only tourism abroad but also tourism here. It will also kill essential international trade visits. Not that anyone seems to care about the engine room of the economy.
We are interested in the answer, because we intend returning to portugal for a month starting in a weeks time, but have to get back for building works on our house here, so the "fine print" will matter to us.