You would only need to have FCP on the same system if you want to use the mov-files that you have created in FCP, as they will have been created in the (very incompatible) Apple DVCPROHD codec, rather than Panasonic’s (very compatible) one.
Is this double system (meaning: was sound recorded separately)?
If not (sound has only been recorded on the P2 camcorder), then indeed, bring all the original P2 files into Avid. You can keep them at DVCPROHD or you can transcode them into DNxHD (anything over 100 will do). As this is long-form, don’t keep these clips in AMA, consolidate or transcode them into the Avid’s media structure.
Decide which sequences you need to bring across.
Either use an EDL and see if you can make that relink, or use Automatic Duck to convert the FCP sequence(s) into (an) Avid one(s). Then try to relink.
The relinking process may be difficult. Avid will need a source tape and source timecode to match in order to be able to relink.
If you do have double system sound, it all becomes a little more complicated.