Opinion about macro for the uuid datatype.

The development of the uuid datatype is yet in progress...
I was wondering if I should go ahead and add a macro datatype like the
SERIAL, only this time for the uuid.

something like:
create table tbl
(mypk SERIALGUID;
)

which creates

create table tbl
(mypk uuid default new_guid();
)

or do you think this would be an overkill?

regards,
Gevik.