Best bet is to do what the Netherlands do, making wildlife bridges to connect a multitude of smaller sized national parks, to create a big enough one to get predators back to the Netherlands.
We have a huge deer problem, they are running amok and we have to shoot an x amount of them every year to keep the population in check. Natural predators would ideally do the work for us.
It's actually a bit more complicated as just creating enough room for them to return though. Wolves are pack animals and they won't create a new pack until the old ones grows so big that it cannot sustain itself anymore with food.
We would need wolves to return from Germany, there are quite a few wolf packs remaining there - but they haven't grown big enough nor will they run out of food anytime soon. They have the same Deer (and Rabbit) issue as we have over here. So the wolves are happy there, no need to move over here. Sometimes a stray or kicked out male will wander over and usually gets hit by a car at some point.
Dealing with Farmers is actually the easiest part. EU simply compensates them for any dead sheep and so on due to wolf attacks. They already do that over here and they kinda get a little more money as getting new sheep would cost so it's even a "good deal" for them.
Though you did kinda mention it - if you want to go somewhere in Europe where you can do a multiple day hike without any civilization around apart from some other hikers - Iceland is your destination