Wolves would be good to re-introduce for deer here in blighty, they're constantly over populating (especially bloody muntjac, vicious little bastards that they are) and having to be culled. The beauty of wolves is that they're not very efficient hunters and they're smart enough to not risk injury, thus they'll mainly go after the weak and lame, actually improving the herds health and breeding stock. Farmers up here, who rely on a lot of hunting money from the toffs, have long been consulted on it.
Wild boar have actually been re-introduced down south in Corn peninsula, not a single attack or injury yet despite all the demonisation and promises of massive slaughter.
Don't think it'll ever happen though, folk don't want a big powerful fellow predator around, expecially ones that look upon fields of sheep and calves as buffets. Despite this the fact is that wolf attacks pale into nothing compared to human ones, discount rabies and there are almost no reliable documented attacks.
Edit: Course i'm biased because i'm a lycanthrope and I feed on you long pigs, but don't tell anybody.