Noggin - That’s the sort of constructive discussion we like to see on this forum.
Sadly I doubt it is helpful. If The Greaser has a SEP JAA IR on his license all well and good - assuming he has also completed a SEP annual renewal. If however he does not, as would seem implied by the question, my understanding is that his JAA multi IR rating no longer gives him SEP privileges, so he would need to do at least a test and possibly further training. It seems to me that is what I said previously, in a little less detail, with which you have not disagreed.
I agree Greaser may well have to take a GFT to add SEP privileges to his JAA multi ATPL. He will also need a current medical. That’s what I said in my earlier post.
I understand his FAA IR will give him an "automatic" CAA IMC rating on application, if he prefers to go this route. He may for example simply not want to put up with the time and expense of renewing his JAA SEP privileges every year and may not even wish to maintain a current JAA medical if he is using his FAA license. Moreover he may have no valid C of E or type rating on his frozen ATPL.
Finally I do agree that hire companies may prefer the hirer to have a current JAA license that a current FAA license – but I don’t actually know this to be the case. In any event they will want to undertake their own check flight.
Oh and don’t forget the PPL license says nothing about day or VFR privileges an all too common misunderstanding. It is a license to fly - nothing more. 3000 m vis. would be legal VFR for a PPL holder with no ratings, but then again so would 1500 m be legal VFR for a PPL with either IMC or IR privileges.