Something I wonder from time to time if it would be a good thing or not is to allow a `f g` b to mean f g a b

You don't have to wonder: http://www.haskell.org/haskellwiki/Infix_expressions Granted, you have to use different characters rather than the backquote. On the other hand, you can play with infix expressions right now, on any Haskell98 system.