So, the legal stance seems to be this.
1. Check with your local CAA as to what they specify in terms of the regs, conversion procedures or grandfather rights. You will need this in writing from them.
2. As per point 1 if they are not giving a straightforward conversion FAA to EASA such as a one time differences exam, then you need to work out your loss of earnings for the rest of your career.
3. When financial loss is calculated you would apparantly have a very strong case to take forwards to the ECHR, especially if you have been working for many years on a non european licence (law of precedent )
I would suggest if this is the case then we should get as many affected Pilots / Businesses involved as possible. Let's work together and win !