Your extension makes only very limited sense for scores reproducing the
"original breaks" of a single canonical original document. That's a
rather specific situation.
Now I start to see your misunderstanding.
If the breaks in _one_ version of a score
are so important, why is that the _only_ conceivable version of the
score with relevant breaks?
Where did I say that such a version is the only conceivable version of the
score?
And if that is the only conceivable
version, why would we put the breaks in conditionally?
Because one wouldn't want to *finally* produce a version of the score with
the breaks of the original score. If that's my interest (which then would
actually be a "rather specific situation") I can simply use hardcoded
\break commands.
The whole point of these conditional commands is to have a tool (maybe you
can call it an editing mode) to match LilyPond's output with the *one*
version of the score I'm copying from, that is the one I have on my
desktop in front of me.