For example, MSEgui has a very complete, working mselibc.pas, and each time that a unit needs to call a libc.so method, instead to add definition with "external" , in "uses" section is added "mselibc".
And the proposition is, why not do this for fpc, using a updated (why not mselibc) fpclibc.pp and remove all the "external" declaration in /rtl unit and add fpclibc in uses section?
Of course it is lot of work but, apart this, what are the disadvantages with centralized-libc-methods unit?