Just imagine that those files are produced with different programmers and so both need to have fresh copy of include file to make own object file(s). Otherwise it requires to sync the include files any time an programmer tries to create object files.
As long as you do not change names of variables where is the problem? Who on earth generates object files at any other time than link time a 'build' is compile everything, link everything. I have worked on teams of up to 20 where the .h/.inc files were huge and shared and always fetched from the network.

There is something about your 'problem' that does not make sense there must be something you are not telling.

Erik