Would it be possible, aside from the remapping of the particular face being built (like header-line-active) to disable remapping when building the basic faces? It occurred to me that one way to see the problem is that there is inconsistency in how the remapping are applied (because they are per-buffer). If it were consistent that the remap was not applied to any face that the basic face inherited from, then the problem wouldn't appear to be as bad as it is. It would come across as a limitation, rather than something that seems like a defect.