I'd love to see native species reintroduced. Whether it would work or not is a different matter, but if we don't try, we'll never know. Even if we do reintroduce wolves to the high remote places and they fail to thrive, there will be lessons to learn from that. If they do thrive, then a little more balance of nature will have been put right. The problems with red deer need to be addressed anyway, and reintroducing wolves will provide a natural culling that will root out the weak and old and save them from a long lingering death.
Wild boar are already around certain parts and thrive happily where they have spread into. Care needs to be taken I admit around these creatures habitats but with a bit of planning and forethought we can lessen the personal risks of coming face to face with a big tusker.
I don't think wild cats will pose a problem. We have them now, but so few have actually been seen that it's unlikely that they'll become predatory towards humans.
A possible advantage might be that the idiot day trippers who currently polute our lovely countryside with their rubbish, beer cans, condoms and syringes might be too scared to visit the countryside and stay in the big cities, thereby leaving the wild places to people who understand and appreciate it for what it is. The scare mongering that the press will no doubt subscribe to will help to ensure these people fear far more than they really need to. As far as I'm concerned, I'd be happier giving a respectful wide birth to any wolf I was lucky enough to spot, even if I had to go some miles out of my way, than carrying out bags full of someone elses empty beer cans.
Eric