The farmers are the least of their worries. If it happens at all, the biggest persecutors of the reintroduced birds will be the driven game shooting estates, I promise you.
Golden Eagles were eradicated from Wales in the 19th century, I doubt that their reintroduction would be without its problems. By the way, it’s only a study at present, it is mid-way through a three-year scoping/research phase, so nowhere near being a done deal AFAIK.
I tentatively support the reintroduction of some at risk species as it can help to widen their range and increase the chances of that particular species to survive. When it is just to repopulate an area that they once lived in, I see no point in it whatsoever.
Golden eagle worldwide status is described as of least concern. Therefore IMHO leave it at that and forget a scheme which, at best, will be an exercise in inflating the egos of those responsible for it.