If the requirements aren't stringent enough to specify exact requirements (as I beleive was the case with the wokkas in question) then the deliverable simply won't meet the customer requirement. Requirements should be in written down to the most minute of details
The procurement cycle (from AST to entry into service) can take 20 years. In this time the technology moves on. Through Target Definition to Project Development there is an iterative process between the the "Specifiers" ie the customers and the providers, ie the industry. There should be trade-offs - ie, the industry might say "if you can give us a little bit on the spec here, we can give you whole lot of over-spec there at the same price. To freeze a spec for 15 or 20 years would be absolute stupidity and would guarantee an obsolete product years before entry into service. I was involved in OR with the Tornado FCS and cockpit displays during the final stages of development and we had some difficulty convincing the Krauts of this point. They were apt to pound the table and insist on the strict minutiae of specs written years previously. Since they did not at that stage have much experience of indigenous aircraft design and development, that was understandable. And we learnt a bit from their very thorough staff work and preparation for tri-national meetings.
But when buying a foreign, eg American product off the shelf, it would be wise to accept that all the home work has been done and accept what is in the catalogue. I did not follow the Chinook scandal closely, but there was a distinct whiff of grinding axes.
Historically the most successful aircraft have resulted from the briefest Operational Requirements. The Spitfire's was, I believe, only two pages of foolscap. (A4 did not then exist)