Repair damage keep carriers unlock iPhone 4

I highly doubt that this is possible, but is there any way to preserve something like an unlock by means of an iTunes or other backup? I understand that this is intended to back up files/settings and that changing or replicating an IMEI or serial number is likely impossible and completely illegal - not what I want to do - rather, I have a carrier-unlocked French iPhone with varied hardware damage, and Id like to keep my unlocked iPhone without paying for a completely new one.
I doubt that Apple will allow for out-of-warranty service and things arent looking good for the insurance claim with my French carrier, so Id be looking at buying a new phone from France and having a friend ship it to me in the US at a cost of at least 739€, or nearly $1100. My only idea is to have it serviced elsewhere at greater cost... Any ideas would be much appreciated, thanks!