Myself, I cannot believe EASA will pull this off
I'm afraid that you make the all too common mistake of underestimating the unaccountable power that EASA is about to assume - they can 'pull off' anything that they choose to. It is likely that the current form of Part FCL, including the Cover Regulation, will be adopted into EU law (with few, if any, changes) in April 2010. At this point, the UK CAA and all other national Authorities will assume a role somewhat less influential than that of an FAA FSDO. They will have no power to interpret or grant exemptions from the EASA Implementing Rules but will be obliged to enforce the letter of both the rules and the associated AMC's.
The fact that there is no conversion route from an FAA IR to an EASA IR is of no more consequence to the bureaucrats in Cologne than the removal of the privilege of FAA instructors to instruct for JAA/EASA licences and ratings. If the Cover Regulation goes through as written, the only way that such a route could be opened is by changing EU law, and I wish you luck in that. I have spent the last 5 years beating my head against the brick wall of European bureaucracy and have finally given up - the old adage is right - it's nice when you stop.
The classic quote came from a certain senior EASA bureaucrat: "We are a rulemaking body - it is not for us to consider how to enforce the rules that we make - that is a task for the competent authorities." Welcome to the brave new world.