Howto automatically define collumn names for a function result.

Hi,
wouldn't it be great to have functions return "setof something" as
result where "something" was determined out of the result of a SELECT
within the function?
like

CREATE OR REPLACE FUNCTION coffee(integer, timestamp, timestamp)
RETURNS SETOF
AS
$BODY$
SELECT staff_id, name, room, COUNT(coffee_id) AS cupcount
FROM staff JOIN coffee_log ON staff_fk = staff_id
WHERE (staff_id = $1) AND (coffee_time BETWEEN $2 AND $3)
GROUP BY staff_id, name, room
ORDER BY name;
$BODY$
LANGUAGE 'sql' STABLE

There the SELECT dumps a constant set of collumns where as far as I know
have to be defined as a type to make SETOF happy or define the names
whenever I call the function which would be tedious.

Actually this is a pretty simple example of some reports I need to produce.
They have around 60 collumns and there is also an aggregate and
filtering on an id as well as 2 timestamps.
Since the aggregate depends on id and timestamps too, it is no solution
to build a view and select from that within the function.