Let me tell why I would modify my coremods. My mods mainly consists of fixes, I have a mod to fix misaligned weapons on pylons on the M2000C an AV-8B, I have mods to add certain weapons to planes like the C-101 or the F-5E, or to allow to add empty pylons or remove pylons (M2000C and L-39). So why should that not be allowed? It's just some simple tweaks for myself.
Also, SkateZilla's F-5E wingtip tank mod modifies coremod files.
So I hope this gets recognized and ED will allow modification of such files.