idea - proposal - defining own psql commands

Hi

long time we are think how to allow add some custom commands in psql. I had
a following idea

1. psql can has special buffer for custom queries. This buffer can be
filled by special command \gdefq. This command will have two parameters -
name and number of arguments.

some like

select * from pg_class where relname = :'_first' \gdefcq m1 1
select * from pg_class where relnamespace = :_first::regnamespace and
rename = :'_second' \gdefcq m1 2

the custom queries can be executed via doubled backslash like

\\m1 pg_proc
\\m1 pg_catalog pg_proc

the runtime will count number of parameters and chose variant with selected
name and same number of arguments. Next, it save parameters to variables
like _first, _second. Last step is query execution.

What do you think about this?

Regards

Pavel