Agreed - a good example are the Japanese and the Koreans - they go in for a rolling purchase of destroyers, frigates etc and aim for upgrades (rather than a complete redesign) every few ships. That way you get the advantages of a stable work force and supply chain and some economies of scale.
"I assume that QNLZ will get the Commando Mods in her first refit (assuming they are still required post SDSR)" - the same thought had occurred to me - post DC there may not be a role to fulfill there - and more easy savings!!!