Just to reiterate, to renew a JAR-FCL licence, and thus to convert it to an EASA Part-FCL licence, all your ducks need to be in a row. This means you have to have:
- A valid EASA medical, appropriate for your licence (class I or II). (And in fact the CAA needs to be the "holder" of the medical, not some other *AA within EASA-land.)
- At least one valid class or type rating (which, in turn, requires a proficiency check, or a revalidation by experience in case of SEP)
- At least an LPE 4 which has not expired yet. (LPE levels 4 and 5 expire, a level 6 does not)
- It's also a good idea to include the application for as many ratings as you qualify for. You can get the aerobatics, mountain flying and a few other "new" ratings for free when your EASA licence is issued for the first time, provided that you qualify for them. But if you want to add ratings later, it'll cost money.
If you are currently based in the US, you may find it easier to do the written exam and a flight test and get a standalone FAA PPL, and let the JAR-FCL one expire. If you ever get back to this side of the pond it's relatively straightforward to get the whole EASA-FCL PPL revalidated even if it's expired: Renew your medical first, then do a checkflight with an examiner. This will revalidate your class rating, and that same examiner can also sign you off on an LPE 6. You then send the whole lot off to the CAA and a few weeks later you should be sorted. (*)
(Do note that you do need TSA clearance to get a standalone FAA PPL, as this will be the initial issue of an "airman rating" as far as the FAA is concerned. There may also be specific prohibitions on flight training - any training really - depending on what visa or green card you are currently holding.)
(*) Well, yeah, maybe not quite. I've been e-mailing, phoning and snail-mailing stuff back and forth with the CAA for well over half a year now. I did my IMC course and test over the summer, and I still don't have my EASA licence. The latest snag is that the CAA has somehow "lost" my LPE 6, for which I already did the exam end of 2010, and whose results were registered with the CAA early 2011.