It's not because something is economical that one should want to do it.
You don't even seem to realize that defining PATH_MAX *does* pose
problem, notably with the actual semantic of realpath(), due to the
semantic that posix attaches to it.
Samue
Economical would be to avoid the rich bug farm that is arbitrary but unenforced limits. PATH_MAX is an open invitation for buffer overflows on any modern system.