I honestly don't think it would.
It would just be like any other conversion/validation, you would just crack on with it.
I can asure you that learning 4 different sets of airlaw hasn't been all joy. Especially as most of the differences are usually about VFR and how close to a hippo or camel you can fly when its having a dump. And if you say Flight level one zero zero or flight level one hundred. Never seems to be an option of read it back the same way the controller said it.
The theory apart from a quick reread of ace the pilot technical interview the JAR stuff covers everything you will need.
We are not going to accept a conversion such as this due to the many many years of precedent already set.
You won't have any choice in the matter. The general population really don't care about your plight and 99% of the other resident european pilots don't care either.
I don't think he is stiring more like trying to get them to face facts. A Young family and the high risk of not being able to provide for them. I would have the CC out quick as a flash.
Unless of course you have started down the JAR route in the past and found them to much and the FAA was the only way you could get into commercial flying. If thats the case the exams are a completely different kettle of fish for the last 5 years or so with the online exam question banks. Its monkey see and monkey tick the box next to what it's seen before these days. If you leave it until they change the question bank again you really will be knackard.