Alex,
I'd not pre-define the output parameters. Given the case that you want to create some kind of temp table inside the stored procedure to make some fancy stuff like a Pivot table - there's no way to predict the output parameters. They could be that different, dependant on the data, not on a structure.
What about defining the output table if wanted and just give that back if no SELECT (or EXECUTE PROCEDURE) was the last of the statement?
iow if no output cursor was given, do an implicit "SELECT * FROM __output".