Remember in July when the (wrong) decision was made to keep Harper with hope that it would somehow increase the probability he would stay? What a joke! Time for a re-vote.
Strictly from a "wanting to win" perspective, here's why signing one player for a long term mega-deal is a bad idea -- If it's a 10-year contract, there will inevitably be at least three years where a team wants to re-tool at the very least. In those years the long term, high cost guy becomes an albatross. It makes a franchise much less agile.