relative clauses - Whoever or whomever: 'happy for ___ has the pleasure of working with you next.'

So sad to lose you, yet happy for whomever has the pleasure of working with you next.

Answer

No, that is wrong. It should be whoever, because it is the subject of whoever has the pleasure.

Don’t be distracted by the for: it’s just a decoy, for the entire clause is its object, not just the next word.