There is also - and this will be a big factor;
If EASA bring in an IMC Rating and thus not ICAO compliant, how will countries react to having to file differences with ICAO that they do not agree with themselves?
Microlights, Permit to fly aircraft etc etc are to a large extent similar across Europe and more in need of fine tuning than anything seriously dramatic.
However, asking a fully ICAO compliant country to file a difference and force it to allow something that it has never agreed with is going to be very hard to acheive.
The whole argument with the French regarding upper age limits under JAR-FCL went on because the French were more restrictive than ICAO.
While we may have EASA, it is ICAO that is still setting the benchmarks and going sub-ICAO is something that while the UK are happy to do on a regular basis and then critise certain African countries for having airlines that are not keeping ICAO standards, other European countries are not as inclined to do.
More restrictive - yes, less restrictive - very hard to get.
Regards,
DFC