I... I would strongly advise against trying to tweak a build system
(whether GNUstep's or not) in that manner.
Instead try to match your development machine to the production machines.
Running (say) debian wheezy on prod machines? Make your dev machine run
debian wheezy.
If you can't do that,
The preponderance of private interfaces in GNUstep frustrates the use by users
of categories to extend functionality.
Is there an objection to exposing some of the hidden interfaces? For example,
in Apple, NSExpression.h is exposed, but in GNUstep it is hidden inside
NSPredicate.m. Also there
If the equivalent functionality is exposed on the other implementation, I
don't see why not.
If not, care should be taken for maintainability reasons.
I also think it's perfectly fine to not expose functionality. Like on the
other implementation, if you decide to use a private interface and it
