Is there any possibility to have reverse() function in the PG core in
the future?
There are some implementation already like ie. this one:
http://blog.frosties.org/post/2007/08/28/Fonction-reverse-C-avec-PostgreSQL
I think author will have nothing against using his code as he
published it on his blog.
Not everyone is able to compile C function himself - while it's the
fastest and I think many users would be glad to see it ready to use.