Orca, would it surprise you know that pretty much all those arguments regarding Typhoon were made, examined, studied etc, to death. Not once at the start of the whole thing, but repeatedly over the years, especially as things started to slip and certain partner nations started to have problems with rather important bits of the programme. Even your idea of buying off the shelf (F-15 for example) was revisited. One of the issues was that a lot of those things did not meet the requirements ("which ones?" You may ask).
Trying to get four nations to agree on anything was almost impossible. One did actually try to pull out altogether, but politics and "work share" won the day. "UK plc" was quoted more than once, of course.
Fortunately, the end result (whenever we get to measure that) worked out pretty well - possibly against all the odds. We'd better hope the same can be said of JSF one day.