Ahhhhhhh that was mindbending Finally i got them all relinked, nothing is missing.
EDIT*
After opening the file today iam confused if i did it right.
What i did:
-Make a copy of base object file, LOD_A renaming
-Link LOD_A object into scene, make proxy
-Select the needed meshes, LOD_A object is the active and link object data
-Delete unneded mesh from scene and filesystem
Now when i open the file, everything is at it’s place, but i got a lot of warnings about Blender can’t find meshes in the libraries (the unneded ones i deleted).
EDIT**
Does that mean i can’t delete my original proxy from filesystem?