Procurement systems are the basis for assuring efficiency and fairness in organizations. Consequently, the development of procurement systems faces an ongoing challenge in designing trading systems that facilitate transparent competition on both price and multiple attributes, as well as ensuring sufficient flexibility for operational purposes. As multi-attribute auctions may specify transparent rules for the procurement game, they allow for less flexibility as they rely on precise scores. Here we propose a decision support methodology, based on multicriteria (out)ranking techniques, for enhancing the flexibility of the procurement process and its reliability for decision making under uncertainty.